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A Photoelectrochemical Solar Cell: An Undergraduate Experiment.
ERIC Educational Resources Information Center
Preparation and testing of a cadmium selenide photoelectrical solar cell was introduced into an environmental chemistry course to illustrate solid state semiconductor and electrochemical principles. Background information, procedures, and results are provided for the experiment which can be accomplished in a three- to four-hour laboratory session�
Boudreau, Sharon M.; And Others
Results from the IMP-J violet solar cell experiment and violet cell balloon flights
NASA Technical Reports Server (NTRS)
The IMP-J violet solar cell experiment was flown in an orbit with mild thermal cycling and low hard particle radiation. The results of the experiment show that violet cells degrade at about the same rate as conventional cells in such an orbit. Balloon flight measurements show that violet solar cells produce approximately 20% more power than conventional cells.
Gaddy, E. M.
A Dust Characterization Experiment for Solar Cells Operating on Mars
NASA Technical Reports Server (NTRS)
During the Viking and Pathfinder missions to Mars, significant amounts of dust accumulated on the spacecrafts. In Pathfinder's case, the dust obscured the solar panels on the lander and the rover degrading their output current. The material adherence experiment aboard the Pathfinder rover quantified the rate of decrease in short circuit current at 0.28% per day. This rate is unacceptably high for long duration missions. In response, NASA has developed the Dust Accumulation and Removal Technology (DART) experiment. DART has three instruments for characterizing dust settling out of the atmosphere and tests two methods to keep dust from settling on solar cells.
Jenkins, Phillip; Landis, Geoffrey A.; Krasowski, Michael; Greer, Lawrence; Wilt, David; Baraona, Cosmo; Scheiman, David; Lekki, John
Solar cell experiments for space: past, present and future
NASA Astrophysics Data System (ADS)
Since the early beginnings of the space age in the 1950s, solar cells have been considered as the primary choice for long term electrical power generation of satellites and space systems. This is mainly due to their high power/mass ratio and the good scalability of solar modules according to the power requirements of a space mission. During the last decades, detailed solar cell material studies including the non-trivial interaction with high-energy space particles have led to continuous and significant improvements in device efficiency. This allowed the powering of advanced space systems like the International Space Station, rovers on the Martian surface as well as satellites which have helped to understand the universe and our planet. It is noteworthy that in addition to their success in space, these photovoltaic technologies have also broken ground for the application of photovoltaic systems in terrestrial systems. This paper discusses the development of space solar cells, gives insight into related experiments like the analysis of the interaction with space particles and provides an overview on challenges and requirements for future space missions.
Hoheisel, R.; Messenger, S. R.; Lumb, M. P.; Gonzalez, M.; Bailey, C. G.; Scheiman, D. A.; Maximenko, S.; Jenkins, P. P.; Walters, R. J.
Three year performance of the NTS-2 solar cell experiment
NASA Technical Reports Server (NTRS)
Twelve different solar cell modules from the NTS 2 experiment are functioning after more than three years in a severe trapped radiation orbit of 20,367 km (10,990 nm) circular, 63 deg inclination. The rate of maximum power degradation may be fit to a predicted rate which is based on twice the value of 1 MeV electron equivalent damage fluence calculated from the space electron model AEI 7. The photovoltaic parameters of the cells are compared to their original values to demonstrate rank order of performance.
Statler, R. L.; Walker, D. H.
Experiment Based Teaching of Solar Cell Operation and Characterization Using the SolarLab Platform
interfaces for exploring different solar cell principles and topics. The exercises presented in the current (MSc and PhD level) taught at the Department of Energy Technology, Aalborg University. SOLAR CELL), presented in detail in [1], where: I is the output current of the solar cell; V - terminal voltage; Iph
Sera, Dezso
Light Trapping for Silicon Solar Cells: Theory and Experiment
NASA Astrophysics Data System (ADS)
Crystalline silicon solar cells have been the mainstream technology for photovoltaic energy conversion since their invention in 1954. Since silicon is an indirect band gap material, its absorption coefficient is low for much of the solar spectrum, and the highest conversion efficiencies are achieved only in cells that are thicker than about 0.1 mm. Light trapping by total internal reflection is important to increase the optical absorption in silicon layers, and becomes increasingly important as the layers are thinned. Light trapping is typically characterized by the enhancement of the absorptance of a solar cell beyond the value for a single pass of the incident beam through an absorbing semiconductor layer. Using an equipartition argument, in 1982 Yablonovitch calculated an enhancement of 4n2 , where n is the refractive index. We have extracted effective light-trapping enhancements from published external quantum efficiency spectra in several dozen silicon solar cells. These results show that this "thermodynamic" enhancement has never been achieved experimentally. The reasons for incomplete light trapping could be poor anti-reflection coating, inefficient light scattering, and parasitic absorption. We report the light-trapping properties of nanocrystalline silicon nip solar cells deposited onto two types of Ag/ZnO backreflectors at United Solar Ovonic, LLC. We prepared the first type by first making silver nanparticles onto a stainless steel substrate, and then overcoating the nanoparticles with a second silver layer. The second type was prepared at United Solar using a continuous silver film. Both types were then overcoated with a ZnO film. The root mean square roughness varied from 27 to 61 nm, and diffuse reflectance at 1000 nm wavelength varied from 0.4 to 0.8. The finished cells have a thin, indium-tin oxide layer on the top that acts as an antireflection coating. For both backreflector types, the short-circuit photocurrent densities J SC for solar illumination were about 25 mA/cm2 for 1.5 micron cells. We also measured external quantum efficiency spectra and optical reflectance spectra, which were only slightly affected by the back reflector morphology. We performed a thermodynamic calculation for the optical absorptance in the silicon layer and the top oxide layer to explain the experimental results; the calculation is an extension of previous work by Stuart and Hall that incorporates the antireflection properties and absorption in the top oxide film. From our calculations and experimental measurements, we concluded that parasitic absorption in this film is the prominent reason for incomplete light trapping in these cells. To reduce the optical parasitic loss in the top oxide layer, we propose a bilayer design, and show the possible benefits to the photocurrent density.
Zhao, Hui
Results of the first 150 days of the NTS-1 solar cell experiments
Twelve solar cell experiments were on the Naval Research Laboratory NTS-1 satellite launched on 14 July 1974, into a 13,260 km circular orbit at an inclination of 125 deg. The experiment comprises: 2 ohm-cm n\\/p, lithium-diffused p\\/n, violet n\\/p, p(+) back surface field, and ultra-thin wrap around contact cells. The short-circuit current of the experiments ranged from 2 to 12
R. L. Statler
NASA Technical Reports Server (NTRS)
The results of post-flight performance testing of the solar cells flown on the Advanced Photovoltaic Experiment are reported. Comparison of post-flight current-voltage characteristics with similar pre-flight data revealed little or no change in solar cell conversion efficiency, confirming the reliability and endurance of space photovoltaic cells. This finding is in agreement with the lack of significant physical changes in the solar cells despite nearly six years in the low Earth orbit environment.
Brinker, David J.; Hickey, John R.; Scheiman, David A.
NASA Technical Reports Server (NTRS)
The results of the postflight analysis of the solar cell assemblies from the LDEF (Long Duration Exposure facility) experiment A0171 is provided in this NASA sponsored research project. The following data on this research are provided as follows: (1) solar cell description, including, substrate composition and thickness, crystal orientation, anti-reflective coating composition and thickness; (2) preflight characteristics of the solar cell assemblies with respect to current and voltage; and (3) post-flight characteristics of the solar cell assemblies with respect to voltage and current. These solar cell assemblies are part of the Goddard Space Flight Center test plate which was designed to test the space environment effects (radiation, atomic oxygen, thermal cycling, meteoroid and debris) on conductively coated solar cell coversheets, various electrical bond materials, solar cell performance, and other material properties where feasible.
Hill, David C.; Rose, M. Frank
NASA Technical Reports Server (NTRS)
Emerging satellite designs require increasing amounts of electrical power to operate spacecraft instruments and to provide environments suitable for human habitation. In the past, electrical power was generated by covering rigid honeycomb panels with solar cells. This technology results in unacceptable weight and volume penalties when large amounts of power are required. To fill the need for large-area, lightweight solar arrays, a fabrication technique in which solar cells are attached to a copper printed circuit laminated to a plastic sheet was developed. The result is a flexible solar array with one-tenth the stowed volume and one-third the weight of comparably sized rigid arrays. An automated welding process developed to attack the cells to the printed circuit guarantees repeatable welds that are more tolerant of severe environments than conventional soldered connections. To demonstrate the flight readiness of this technology, the Solar Array Flight Experiment (SAFE) was developed and flown on the space shuttle Discovery in September 1984. The tests showed the modes and frequencies of the array to be very close to preflight predictions. Structural damping, however, was higher than anticipated. Electrical performance of the active solar panel was also tested. The flight performance and postflight data evaluation are described.
NASA Technical Reports Server (NTRS)
The Heat Exchanger Method (HEM) produces high efficiency crystal ingots in an automated well-insulated furnace offering low equipment, labor and energy costs. The "grown" silicon crystals are used to make solar cells, or photovoltaic cells which convert sunlight directly into electricity. The HEM method is used by Crystal Systems, Inc. and was developed under a NASA/Jet Propulsion Laboratory contract. The square wafers which are the result of the process are sold to companies manufacturing solar panels.
NSDL National Science Digital Library
This NOVA video podcast is about Germany's solar experiment. Munich's solar panel farm lines the Autobahn and countryside in a massive effort to prove solar's feasibility as a practical renewable energy source.
Two years of on-orbit gallium arsenide performance from the LIPS solar cell panel experiment
NASA Technical Reports Server (NTRS)
The LIPS on-orbit performance of the gallium arsenide panel experiment was analyzed from flight operation telemetry data. Algorithms were developed to calculate the daily maximum power and associated solar array parameters by two independent methods. The first technique utilizes a least mean square polynomial fit to the power curve obtained with intensity and temperature corrected currents and voltages; whereas, the second incorporates an empirical expression for fill factor based on an open circuit voltage and the calculated series resistance. Maximum power, fill factor, open circuit voltage, short circuit current and series resistance of the solar cell array are examined as a function of flight time. Trends are analyzed with respect to possible mechanisms which may affect successive periods of output power during 2 years of flight operation. Degradation factors responsible for the on-orbit performance characteristics of gallium arsenide are discussed in relation to the calculated solar cell parameters. Performance trends and the potential degradation mechanisms are correlated with existing laboratory and flight data on both gallium arsenide and silicon solar cells for similar environments.
Francis, R. W.; Betz, F. E.
Materials on the International Space Station - Forward Technology Solar Cell Experiment
NASA Technical Reports Server (NTRS)
This paper describes a space solar cell experiment currently being built by the Naval Research Laboratory (NRL) in collaboration with NASA Glenn Research Center (GRC), and the US Naval Academy (USNA). The experiment has been named the Forward Technology Solar Cell Experiment (FTSCE), and the purpose is to rapidly put current and future generation space solar cells on orbit and provide validation data for these technologies. The FTSCE is being fielded in response to recent on-orbit and ground test anomalies associated with space solar arrays that have raised concern over the survivability of new solar technologies in the space environment and the validity of present ground test protocols. The FTSCE is being built as part of the Fifth Materials on the International Space Station (MISSE) Experiment (MISSE-5), which is a NASA program to characterize the performance of new prospective spacecraft materials when subjected to the synergistic effects of the space environment. Telemetry, command, control, and communication (TNC) for the FTSCE will be achieved through the Amateur Satellite Service using the PCSat2 system, which is an Amateur Radio system designed and built by the USNA. In addition to providing an off-the-shelf solution for FTSCE TNC, PCSat2 will provide a communications node for the Amateur Radio satellite system. The FTSCE and PCSat2 will be housed within the passive experiment container (PEC), which is an approximately 2ft x2ft x 4in metal container built by NASA Langley Research Center (NASA LaRC) as part of the MISSE-5 program. NASA LaRC has also supplied a thin film materials experiment that will fly on the exterior of the thermal blanket covering the PCSat2. The PEC is planned to be transported to the ISS on a Shuttle flight. The PEC will be mounted on the exterior of the ISS by an astronaut during an extravehicular activity (EVA). After nominally one year, the PEC will be retrieved and returned to Earth. At the time of writing this paper, the subsystems of the experiment are being integrated at NRL, and we are preparing to commence environmental testing.
Walters, R. J.; Garner, J. C.; Lam, S. N.; Vazquez, J. A.; Braun, W. R.; Ruth, R. E.; Lorentzen, J. R.; Bruninga, R.; Jenkins, P. P.; Flatico, J. M.
Photoelectrochemical Solar Cells.
ERIC Educational Resources Information Center
This introduction to photoelectrochemical (PEC) cells reviews topics pertaining to solar energy conversion and demonstrates the ease with which a working PEC cell can be prepared with n-type silicon as the photoanode and a platinum counter electrode (both immersed in ethanolic ferrocene/ferricenium solutions). Experiments using the cell are�
McDevitt, John T.
NASA Technical Reports Server (NTRS)
The Advanced Photovoltaic Experiment (APEX), containing over 150 solar cells and sensors, was designed to generate laboratory reference standards as well as to explore the durability of a wide variety of space solar cells. Located on the leading edge of the Long Duration Exposure Facility (LDEF), APEX received the maximum possible dosage of atomic oxygen and ultraviolet radiation, as well as enormous numbers of impacts from micrometeoroids and debris. The effect of the low earth orbital (LEO) environment on the solar cells and materials of APEX will be discussed in this paper. The on-orbit performance of the solar cells, as well as a comparison of pre- and postflight laboratory performance measurements, will be presented.
Brinker, David J.; Hickey, John R.
NASA Technical Reports Server (NTRS)
The Forward Technology Solar Cell Experiment (FTSCE) is a space solar cell experiment built as part of the Fifth Materials on the International Space Station Experiment (MISSE-5): Data Acquisition and Control Hardware and Software. It represents a collaborative effort between the NASA Glenn Research Center, the Naval Research Laboratory, and the U.S. Naval Academy. The purpose of this experiment is to place current and future solar cell technologies on orbit where they will be characterized and validated. This is in response to recent on-orbit and ground test results that raised concerns about the in-space survivability of new solar cell technologies and about current ground test methodology. The various components of the FTSCE are assembled into a passive experiment container--a 2- by 2- by 4-in. folding metal container that will be attached by an astronaut to the outer structure of the International Space Station. Data collected by the FTSCE will be relayed to the ground through a transmitter assembled by the U.S. Naval Academy. Data-acquisition electronics and software were designed to be tolerant of the thermal and radiation effects expected on orbit. The experiment has been verified and readied for flight on STS-114.
Jenkins, Phillip P.; Krasowski, Michael J.; Greer, Lawrence C.; Flatico, Joseph M.
New solar cell technologies are emerging that could replace silicon cells in power-conversion applications. Gallium arsenide, indium phosphide, and other semiconducting compounds are the focal point of an expanding research effort. The primary subject matter of the article is divided into the following areas: Space vs. terrestrial cell efficiency; Space solar cells; Silicon Cells; Gallium arsenide cells; Other space solar cells; Indium phosphide cells; Superlattice solar cells.
Flood, D.J.
On-orbit performance of LIPS gallium arsenide solar cell experiment
NASA Technical Reports Server (NTRS)
Telemetry from the Living Plume Shield's gallium arsenide solar panel experiment was evaluated to determine degradation. The data were culled to preclude spurious results from possible shadowing or inaccurate measurements on a cold array. Two independent methods were then used to obtain the maximum power points and the various characteristics of the solar array. Fill factor, open circuit voltage, short circuit current, and series and shunt resistances were examined. The data analysis concluded that, to date, nearly all of the solar array degradation is due to the reduction in the short circuit current.
Bavaro, T.; Francis, R.; Pennell, M.
Recent progress in the development of polymer solar cells has improved power-conversion efficiencies from 3% to almost 9%. Based on semiconducting polymers, these solar cells are fabricated from solution-processing techniques and have unique prospects for achieving low-cost solar energy harvesting, owing to their material and manufacturing advantages. The potential applications of polymer solar cells are broad, ranging from flexible solar
Gang Li; Rui Zhu; Yang Yang
ERIC Educational Resources Information Center
Reviews information on solar radiation as an energy source. Discusses these topics: the key photovoltaic material; the bank theory of solids; conductors, semiconductors, and insulators; impurity semiconductors; solid-state photovoltaic cell operation; limitations on solar cell efficiency; silicon solar cells; cadmium sulfide/copper (I) sulfide�
Mickey, Charles D.
Solar array experiments on the Sphinx satellite
NASA Technical Reports Server (NTRS)
The Space Plasma, High Voltage Interaction Experiment (SPHINX) is the name given to an auxiliary payload satellite scheduled to be launched in January 1974. The principal experiments carried on this satellite are specifically designed to obtain the engineering data on the interaction of high voltage systems with the space plasma. The classes of experiments are solar array segments, insulators, insulators with pin holes and conductors. The satellite is also carrying experiments to obtain flight data on three new solar array configurations; the edge illuminated-multijunction cells, the Teflon encased cells and the violet cells.
Stevens, N. J.
Interpretation of Ageing Experiments on CdTe/CdS Solar Cells
ABSTRACT: Thin film CdTe solar cells with different, copper free, contact structures have been subjected to ageing in ambient atmosphere, at 100 �C, under illumination of 1 sun intensity. The cells have been characterised electronically before, during and after ageing by measurement of I-V, C-V and QE(?). Also, SIMS analysis was carried out before and after ageing. This was done to attempt describing ageing in terms of varying electronic properties of the cells, such as doping density or profile, and to correlate this with the observed evolution of the main cell parameters (?, Jsc, V oc, FF). Some cells show an increase in efficiency after ageing, others a decrease. This different behaviour was attributed to a different evolution of the doping profiles upon ageing. The relation between the I-V characteristics and the doping profiles was confirmed with numerical analysis (SCAPS programme). The SIMS results indicate that ageing leads to diffusion and/or accumulation of impurities throughout the absorber, corresponding with the evolution of the doping profiles.
S. Degrave; P. Nollet; G. Stojanoska; M. Burgelman; K. Durose
A novel architecture for high efficiency solar energy conversion, employing separated photo-- and --voltaic pathways and antenna-based light collection, is described. This material-independent architecture solves the ``thick-and-thin'' conundrum of solar photovoltaics, wherein solar cells must be thick enough to absorb light yet thin enough to allow for charge extraction. Our solar cells are comprised of arrays of high aspect ratio,
M. J. Naughton; K. Kempa; Z. F. Ren; J. Rybczynski; T. Paudel; Y. Gao; Y. Xu
A high-efficiency single heterojunction solar cell wherein a thin emitter layer (preferably Ga.sub.0.52 In.sub.0.48 P) forms a heterojunction with a GaAs absorber layer. The conversion effiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the emitter layer.
Olson, Jerry M. (Lakewood, CO)
A high-efficiency single heterojunction solar cell is described wherein a thin emitter layer (preferably Ga[sub 0.52]In[sub 0.48]P) forms a heterojunction with a GaAs absorber layer. The conversion efficiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the emitter layer. 1 fig.
Olson, J.M.
NASA Technical Reports Server (NTRS)
A polymer syrup for encapsulating solar cell assemblies. The syrup includes uncrosslinked poly(n-butyl)acrylate dissolved in n-butyl acrylate monomer. Preparation of the poly(n-butyl)acrylate and preparation of the polymer syrup is disclosed. Methods for applying the polymer syrup to solar cell assemblies as an encapsulating pottant are described. Also included is a method for solar cell construction utilizing the polymer syrup as a dual purpose adhesive and encapsulating material.
Gupta, Amitava (Inventor); Ingham, John D. (Inventor); Yavrouian, Andre H. (Inventor)
NASA Astrophysics Data System (ADS)
This report describes the experimental investigation of the possibility of real-time image compensation of the solar photosphere using the 21-channel Real-Time Atmospheric Compensation (RTAC) system developed at Itek. Observations were made using the 76-cm Vacuum Tower Telescope at Sacramento Peak Observatory in June 1979 and March 1980. During the second period, observations were also made of single and double stars to obtain data on the isoplanatic patch. The compensated image was recorded on videotape using an ISIT camera. In addition, 48 channels of real-time RTAC data (including deformable mirror drive signals) were digitized and recorded on 9-track tape. When observing the sun, it was found that the image stabilization system worked efficiently even with bad turbulence. However, the expected improvement in image sharpness due to the deformable mirror was obtained only on some occasions and could not generally be predicted, in spite of the fact that the RTAC appeared to operate normally with all feedback loops closed and small residual errors. These results appear to be due to atmospheric parameters, primarily the small size of the isoplanatic patch and the small values of turbulence coherence length during the day. This experiment has confirmed the feasibility of real-time compensation of solar images. However, much work remains to be done to refine the technique.
Hardy, J. W.
This text is addressed to upper level graduate students with background in solid state physics and to scientists and engineers involved in solar cell research. The author aims to present fundamental physical principles rather than the state-of-the-art. Specific devices are used to illustrate basic phenomena and to indicate possibilities for innovative design. Contents, abridged: Solar insolation. The calculation of solar
A. L. Farhenbruch; R. H. Bube
Experimenting with Solar Energy
ERIC Educational Resources Information Center
Over the past 25 years, the author has had the opportunity to study the subject of solar energy and to get involved with the installation, operation, and testing of solar energy systems. His work has taken him all over the United States and put him in contact with solar experts from around the world. He has also had the good fortune of seeing some�
Roman, Harry T.
NASA Technical Reports Server (NTRS)
A solar cell shingle was made of an array of solar cells on a lower portion of a substantially rectangular shingle substrate made of fiberglass cloth or the like. The solar cells may be encapsulated in flourinated ethylene propylene or some other weatherproof translucent or transparent encapsulant to form a combined electrical module and a roof shingle. The interconnected solar cells were connected to connectors at the edge of the substrate through a connection to a common electrical bus or busses. An overlap area was arranged to receive the overlap of a cooperating similar shingle so that the cell portion of the cooperating shingle may overlie the overlap area of the roof shingle. Accordingly, the same shingle serves the double function of an ordinary roof shingle which may be applied in the usual way and an array of cooperating solar cells from which electrical energy may be collected.
Forestieri, A. F.; Ratajczak, A. F.; Sidorak, L. G. (inventors)
Sub-bandgap absorption in organic solar cells: experiment and theory.
Most high-performance organic solar cells involve bulk-heterojunctions in order to increase the active donor-acceptor interface area. The power conversion efficiency depends critically on the nano-morphology of the blend and the interface. Spectroscopy of the sub-bandgap region, i.e., below the bulk absorption of the individual components, provides unique opportunities to study interface-related properties. We present absorption measurements in the sub-bandgap region of bulk heterojunctions made of poly(3-hexylthiophene-2,5-diyl) as an electron donor and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as an electron acceptor and compare them with quantum-chemical calculations and recently published data on the external quantum efficiency (EQE). The very weak absorption of the deep sub-bandgap region measured by the ultra-sensitive Photothermal Deflection Spectroscopy (PDS) features Urbach tails, polaronic transitions, conventional excitons, and possibly charge-transfer states. The quantum-chemical calculations allow characterizing some of the unsettled spectral features. PMID:23929440
Beenken, Wichard J D; Herrmann, Felix; Presselt, Martin; Hoppe, Harald; Shokhovets, Sviatoslav; Gobsch, Gerhard; Runge, Erich
NASA Technical Reports Server (NTRS)
The handbook to predict the degradation of solar cell electrical performance in any given space radiation environment is presented. Solar cell theory, cell manufacturing and how they are modeled mathematically are described. The interaction of energetic charged particles radiation with solar cells is discussed and the concept of 1 MeV equivalent electron fluence is introduced. The space radiation environment is described and methods of calculating equivalent fluences for the space environment are developed. A computer program was written to perform the equivalent fluence calculations and a FORTRAN listing of the program is included. Data detailing the degradation of solar cell electrical parameters as a function of 1 MeV electron fluence are presented.
Tada, H. Y.; Carter, J. R., Jr.; Anspaugh, B. E.; Downing, R. G.
Solar molten salt electric experiment
Second generation solar power tower technology, based on using a molten nitrate salt as the solar receiver and thermal storage heat transfer fluid, is now in the final phase of preoperational testing at the Central Receiver Test Facility (CRTF) near Albuquerque, New Mexico. The Molten Salt Electric Experiment (MSEE) is a joint government, electric utility, and industry funded program that
Quantum dot (QD) solar cells have the potential to increase the maximum attainable thermodynamic conversion efficiency of solar photon conversion up to about 66% by utilizing hot photogenerated carriers to produce higher photovoltages or higher photocurrents. The former effect is based on miniband transport and collection of hot carriers in QD array photoelectrodes before they relax to the band edges
A. J Nozik
A photovoltaic solar cell for generating electricity from sunlight is disclosed. The photovoltaic solar cell comprises a plurality of spaced-apart point contact junctions formed in a semiconductor body to receive the sunlight and generate the electicity therefrom, the plurality of spaced-apart point contact junctions having a first plurality of regions having a first doping type and a second plurality of regions having a second doping type. In addition, the photovoltaic solar cell comprises a first electrical contact electrically connected to each of the first plurality of regions and a second electrical contact electrically connected to each of the second plurality of regions, as well as a passivation layer covering major surfaces and sidewalls of the photovoltaic solar cell.
Nielson, Gregory N; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J
Solar cell array interconnects
Electrical interconnects are disclosed for solar cells or other electronic components using a silver-silicone paste or a lead-tin (Pb-Sn) no-clean fluxless solder cream, whereby the high breakage of thin (<6 mil thick) solar cells using conventional solder interconnect is eliminated. The interconnects of this invention employs copper strips which are secured to the solar cells by a silver-silicone conductive paste which can be used at room temperature, or by a Pb-Sn solder cream which eliminates undesired residue on the active surfaces of the solar cells. Electrical testing using the interconnects of this invention has shown that no degradation of the interconnects developed under high current testing, while providing a very low contact resistance value. 4 figs.
Carey, P.G.; Thompson, J.B.; Colella, N.J.; Williams, K.A.
NSDL National Science Digital Library
Based on a NOVA Online lesson, Teachers' Domain presents this interactive activity that provides reading material and animations to help students learn the basics of photovoltaic cells, including how a solar cell converts solar energy into electricity and the components of the unit (silicon layers, metal backing, antireflective coating, and metal conductor strips). On the site, visitors will also find a supplemental background essay, discussion questions, and standards alignment from Teachers' Domain.
Concentrator solar cell research
Research related to concentrator solar cells has produced a new model for series resistance and the beginnings of a powerful device analysis code for personal computers. The Quasi-One-Dimensional series resistance model permits the evaluation and optimization of losses associated with the front surface collection grid of concentrator solar cells, including nonuniform illumination profiles. The Q-1-D model has been incorporated in
P. A. Basore
The silicon-film design achieves high performance by using a dun silicon layer and incorporating light trapping. Optimally designed thin crystalline solar cells (<50 microns thick) have performance advantages over conventional thick devices. The high-performance silicon-film design employs a metallurgical barrier between the low-cost substrate and the thin silicon layer. Light trapping properties of silicon-film on ceramic solar cells are presented and analyzed. Recent advances in process development are described here.
Hall, R.B.; Bacon, C.; DiReda, V.; Ford, D.H.; Ingram, A.E.; Cotter, J.; Hughes-Lampros, T.; Rand, J.A.; Ruffins, T.R.; Barnett, A.M. [Astro Power Inc., Solar Park, Newark, DE (United States)
Solar Dynamics Observatory/ Extreme Ultraviolet Variability Experiment
Solar Dynamics Observatory/ EVE Extreme Ultraviolet Variability Experiment Frequently Asked and model solar extreme ultraviolet irradiance variations due to solar flares, solar rotation, and solar and structure of the Sun. What is solar variability? Solar radiation varies on all time scales ranging from
Mojzsis, Stephen J.
Welded solar cell interconnection
NASA Technical Reports Server (NTRS)
The efficiency of the welding of solar-cell interconnects is compared with the efficiency of soldering such interconnects, and the cases in which welding may be superior are examined. Emphasis is placed on ultrasonic welding; attention is given to the solar-cell welding machine, the application of the welding process to different solar-cell configurations, producibility, and long-life performance of welded interconnects. Much of the present work has been directed toward providing increased confidence in the reliability of welding using conditions approximating those that would occur with large-scale array production. It is concluded that there is as yet insufficient data to determine which of three methods (soldering, parallel gap welding, and ultrasonic welding) provides the longest-duration solar panel life.
Stofel, E. J.; Browne, E. R.; Meese, R. A.; Vendura, G. J.
ERIC Educational Resources Information Center
This article describes a collaborative learning experience in experimental design that closely approximates what practicing statisticians and researchers in applied science experience during consulting. Statistics majors worked with a teaching assistant from the chemistry department to conduct a series of experiments characterizing the variation�
Lawson, John; Aggarwal, Pankaj; Leininger, Thomas; Fairchild, Kenneth
This report describes the experimental investigation of the possibility of real-time image compensation of the solar photosphere using the 21-channel Real-Time Atmospheric Compensation (RTAC) system developed at Itek. Observations were made using the 76-cm Vacuum Tower Telescope at Sacramento Peak Observatory in June 1979 and March 1980. During the second period, observations were also made of single and double stars
J. W. Hardy
NASA Technical Reports Server (NTRS)
Forty cm Sun tracker, consisting of optical telescope and four solar cells, stays pointed at Sun throughout day for maximum energy collection. Each solar cell generates voltage proportional to part of solar image it receives; voltages drive servomotors that keep image centered. Mirrored portion of cylinder extends acquisition angle of device by reflecting Sun image back onto solar cells.
Berdahl, C. M.
NASA Technical Reports Server (NTRS)
Modified solar cell module uses high transmission glass and adhesives, and heat dissipation to boost power per unit area by 25% (9.84% efficiency based on cell area at 60 C and 100 mW/sq cm flux). Design is suited for automatic production and is potentially more cost effective.
Antonides, G. J.; Dillard, P. A.; Fritz, W. M.; Lott, D. P.
On-orbit results of the LIPS 3/InP homojunction solar cell experiment
NASA Technical Reports Server (NTRS)
The flight performance of the NASA indium phosphide homojunction cell module on the LIPS 3 satellite is presented. The experimental objectivewas to measure the InP cell performance in the natural radiation environment in a circular 1100 km altitude orbit inclined 60 degrees. Flight data for the first year is close to expected values. No degradation in the short-circuit current is seen. Details of cell structure and flight module design are discussed.
Brinker, David J.
EE580 Solar Cells Todd J. Kaiser
7/21/2010 1 EE580 Solar Cells Todd J. Kaiser · Lecture 06 · Solar Cell Materials & Structures 1Montana State University: Solar Cells Lecture 6: Solar Cells Solar Cell Technologies · A) Crystalline Silicon · B) Thin Film · C) Group III-IV Cells 2Montana State University: Solar Cells Lecture 6: Solar
Kaiser, Todd J.
An alloy having a large band gap range is used in a multijunction solar cell to enhance utilization of the solar energy spectrum. In one embodiment, the alloy is In.sub.1-xGa.sub.xN having an energy bandgap range of approximately 0.7 eV to 3.4 eV, providing a good match to the solar energy spectrum. Multiple junctions having different bandgaps are stacked to form a solar cell. Each junction may have different bandgaps (realized by varying the alloy composition), and therefore be responsive to different parts of the spectrum. The junctions are stacked in such a manner that some bands of light pass through upper junctions to lower junctions that are responsive to such bands.
Walukiewicz, Wladyslaw (Kensington, CA); Yu, Kin Man (Lafayette, CA); Wu, Junqiao (Richmond, CA); Schaff, William J. (Ithaca, NY)
NASA Astrophysics Data System (ADS)
Photovoltaic solar cells are gaining wide acceptance for producing clean, renewable electricity. This has been based on more than 40 years of research that has benefited from the revolution in silicon electronics and compound semiconductors in optoelectronics. This chapter gives an introduction into the basic science of photovoltaic solar cells and the challenge of extracting the maximum amount of electrical energy from the available solar energy. In addition to the constraints of the basic physics of these devices, there are considerable challenges in materials synthesis. The latter has become more prominent with the need to reduce the cost of solar module manufacture as it enters mainstream energy production. The chapter is divided into sections dealing with the fundamentals of solar cells and then considering five very different materials systems, from crystalline silicon through to polycrystalline thin films. These materials have been chosen because they are all in production, although some are only in the early stages of production. Many more materials are being considered in research and some of the more exciting, polymer and dye-sensitised cells are mentioned in the conclusions. However, there is insufficient space to give these very active areas of research the justice they deserve. I hope the reader will feel sufficiently inspired by this topic to read further and explore one of the most exciting areas of semiconductor science. The need for high-volume production at low cost has taken the researcher along paths not normally considered in semiconductor devices and it is this that provides an exciting challenge.
Irvine, Stuart
NASA Technical Reports Server (NTRS)
A method is presented for predicting the degradation of a solar array in a space radiation environment. Solar cell technology which emphasizes the cell parameters that degrade in a radiation environment, is discussed along with the experimental techniques used in the evaluation of radiation effects. Other topics discussed include: theoretical aspects of radiation damage, methods for developing relative damage coefficients, nature of the space radiation environment, method of calculating equivalent fluence from electron and proton energy spectrums and relative damage coefficients, and comparison of flight data with estimated degradation.
Carter, J. R., Jr.; Tada, H. Y.
NASA Technical Reports Server (NTRS)
Solar cell "modules" are plastic strips coated with thin films of photovoltaic silicon that collect solar energy for instant conversion into electricity. Lasers divide the thin film coating into smaller cells to build up voltage. Developed by Iowa Thin Film Technologies under NASA and DOE grants, the modules are used as electrical supply for advertising displays, battery rechargers for recreational vehicles, and to power model airplanes. The company is planning other applications both in consumer goods and as a power source in underdeveloped countries.
Photovoltaic Experiment Using Light from a Solar Simulator Lamp.
ERIC Educational Resources Information Center
A photovoltaic cell experiment utilizing the convenience of a solar simulating type lamp is described. Insight into the solid state aspect of a solar cell is gained by the student in studying the characteristics, and deducing from them cell parameters and efficiency. (Author/CS)
Chow, R. H.
Amorphous semiconductor solar cell
A solar cell comprising a back electrical contact, amorphous silicon semiconductor base and junction layers and a top electrical contact includes in its manufacture the step of heat treating the physical junction between the base layer and junction layer to diffuse the dopant species at the physical junction into the base layer.
Dalal, Vikram L. (Newark, DE)
ERIC Educational Resources Information Center
The design and function of solar cells as a source of electrical power for unmanned space vehicles is described in this pamphlet written for high school physical science students. The pamphlet is one of the NASA Facts Science Series (each of which consists of four pages) and is designed to fit in the standard size three-ring notebook. Review�
National Aeronautics and Space Administration, Washington, DC.
NASA Technical Reports Server (NTRS)
Improved design for thin, lightweight solar photovoltaic cells with front contacts reduces degradation of electrical output under exposure to energetic charged particles (protons and electrons). Increases ability of cells to maintain structural integrity under exposure to ultraviolet radiation by eliminating ultraviolet-degradable adhesives used to retain cover glasses. Interdigitated front contacts and front junctions formed on semiconductor substrate. Mating contacts formed on back surface of cover glass. Cover glass and substrate electrostatically bonded together.
Brandhorst, Henry W., Jr.; Weinberg, Irving
The energy generated by solar cells can be transformed into ac power by means of inverters. In most cases these inverters cannot be tested under real conditions, since large solar-cell arrays are not yet available at reasonable prices. Therefore, a circuit that simulates a solar-cell array has been developed.
D. Baert
Solar array flight experiment/dynamic augmentation experiment
NASA Technical Reports Server (NTRS)
This report presents the objectives, design, testing, and data analyses of the Solar Array Flight Experiment/Dynamic Augmentation Experiment (SAFE/DAE) that was tested aboard Shuttle in September 1984. The SAFE was a lightweight, flat-fold array that employed a thin polyimide film (Kapton) as a substrate for the solar cells. Extension/retraction, dynamics, electrical and thermal tests, were performed. Of particular interest is the dynamic behavior of such a large lightweight structure in space. Three techniques for measuring and analyzing this behavior were employed. The methodology for performing these tests, gathering data, and data analyses are presented. The report shows that the SAFE solar array technology is ready for application and that new methods are available to assess the dynamics of large structures in space.
Young, Leighton E.; Pack, Homer C., Jr.
EE580 Solar Cells Todd J. Kaiser
7/21/2010 1 EE580 Solar Cells Todd J. Kaiser · Lecture 08 · Solar Cell Characterization 1Montana State University: Solar Cells Lecture 8: Characterization Solar Cell Operation n Emitter p Base Rear completing the circuit 2Montana State University: Solar Cells Lecture 8: Characterization Solar Cell
Kaiser, Todd J.
Solar PV- How A Solar Cell Works
NSDL National Science Digital Library
The Advanced Technology Environmental and Energy Center (ATEEC) provides this document which will help instructors or anyone who would like to understand the basics of solar power and solar cells. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.
Levander, Alejandro
Coating Processes Boost Performance of Solar Cells
NASA Technical Reports Server (NTRS)
NASA currently has spacecraft orbiting Mercury (MESSENGER), imaging the asteroid Vesta (Dawn), roaming the red plains of Mars (the Opportunity rover), and providing a laboratory for humans to advance scientific research in space (the International Space Station, or ISS). The heart of the technology that powers those missions and many others can be held in the palm of your hand - the solar cell. Solar, or photovoltaic (PV), cells are what make up the panels and arrays that draw on the Sun s light to generate electricity for everything from the Hubble Space Telescope s imaging equipment to the life support systems for the ISS. To enable NASA spacecraft to utilize the Sun s energy for exploring destinations as distant as Jupiter, the Agency has invested significant research into improving solar cell design and efficiency. Glenn Research Center has been a national leader in advancing PV technology. The Center s Photovoltaic and Power Technologies Branch has conducted numerous experiments aimed at developing lighter, more efficient solar cells that are less expensive to manufacture. Initiatives like the Forward Technology Solar Cell Experiments I and II in which PV cells developed by NASA and private industry were mounted outside the ISS have tested how various solar technologies perform in the harsh conditions of space. While NASA seeks to improve solar cells for space applications, the results are returning to Earth to benefit the solar energy industry.
Very high efficiency solar cells
NASA Astrophysics Data System (ADS)
The Defense Advanced Research Projects Agency has initiated the Very High Efficiency Solar Cell (VHESC) program to address the critical need of the soldier for power in the field. Very High Efficiency Solar Cells for portable applications that operate at greater than 55 percent efficiency in the laboratory and 50 percent in production are being developed. We are integrating the optical design with the solar cell design, and have entered previously unoccupied design space that leads to a new architecture paradigm. An integrated team effort is now underway that requires us to invent, develop and transfer to production these new solar cells. Our approach is driven by proven quantitative models for the solar cell design, the optical design and the integration of these designs. We start with a very high performance crystalline silicon solar cell platform. Examples will be presented. Initial solar cell device results are shown for devices fabricated in geometries designed for this VHESC Program.
Barnett, Allen; Kirkpatrick, Douglas; Honsberg, Christiana
Solar thermal propulsion experiments design
Satellites that are currently under powered or have low photovoltaic (PV) efficiency, may be rejuvenated by dosing them with laser power beamed from earth. Also, current strictly solar thermal propulsion schemes may be able to use laser power as a replacement energy source when they are eclipsed. Several questions must be answered before a multiple use of laser power may be designed. The questions are outlined in the background section of this paper. They deal with gains that may be realized using solar power for operating specific hardware as opposed to laser power. A series of experiments that will give the authors information they can use to answer the questions will be performed. However, this paper outlines and presents only the design of experiments based upon statistical methods generated by Dr. Genuchi Taguchi.
Laug, K.K. [Phillips Lab., Edwards AFB, CA (United States)
Status of solar neutrino experiments
A summary of the status of four solar neutrino experiments is presented. The Homestake {sup 37}Cl data are presented and the possible time dependence of the data is addressed. Data from 1040 days of operation of the Kamiokande II detector are presented next. The status of the {sup 71}Ga experiment in the Baksan Neutrino Observatory, which has operated for a short time, is discussed. The summary concludes with a discussion of the status of the Sudbury Neutrino Observatory, which has been under construction since the beginning of 1990. 7 refs., 6 figs.
Beier, E.W.; Davis, R. Jr.; Kim, S.B. (Pennsylvania Univ., Philadelphia, PA (USA). Dept. of Physics); Elliott, S.R. (Los Alamos National Lab., NM (USA)); Jelley, N. (Oxford Univ. (UK))
This paper describes a high efficiency solar cell, it comprises: a germanium substrate having a front surface and a back surface; a back-metal contact on the back surface of the substrate; a buffer layer having a photovoltaic inhibited junction with the front surface of the substrate; the cell including a gallium-arsenide base of one conductivity type on the buffer layer; a gallium-arsenide emitter of the other conductivity type on the base; metal grid lines extending over and being coupled to the emitter.
Ho, F.F.; Linda, Y.; Yeh, M.Y.
Solar cell radiation handbook. Addendum 1: 1982-1988
The Solar Cell Radiation Handbook (JPL Publication 82-69) is updated. In order to maintain currency of solar cell radiation data, recent solar cell designs have been acquired, irradiated with 1 MeV electrons, and measured. The results of these radiation experiments are reported.
Anspaugh, B.E.
Solar Week: Learning from Experience
Solar Week is a week-long set of games and activities allowing students to interact directly with solar science and solar scientists. Solar Week was developed as a spin-off of the highly successful Yohkoh Public Outreach Project (YPOP). While YPOP provided access to solar images, movies and activities, the main goal of Solar Week was to enhance the participation of women,
D. Alexander; K. Hauck
Laser-assisted solar cell metallization processing
NASA Technical Reports Server (NTRS)
Laser assisted processing techniques utilized to produce the fine line, thin metal grid structures that are required to fabricate high efficiency solar cells are investigated. The tasks comprising these investigations are summarized. Metal deposition experiments are carried out utilizing laser assisted pyrolysis of a variety of metal bearing polymer films and metalloorganic inks spun onto silicon substrates. Laser decomposition of spun on silver neodecanoate ink yields very promising results. Solar cell comb metallization patterns are written using this technique.
Dutta, S.
Solar cell module lamination process
A solar cell module lamination process using fluoropolymers to provide protection from adverse environmental conditions and thus enable more extended use of solar cells, particularly in space applications. A laminate of fluoropolymer material provides a hermetically sealed solar cell module structure that is flexible and very durable. The laminate is virtually chemically inert, highly transmissive in the visible spectrum, dimensionally stable at temperatures up to about 200.degree. C. highly abrasion resistant, and exhibits very little ultra-violet degradation.
Carey, Paul G. (Mountain View, CA); Thompson, Jesse B. (Brentwood, CA); Aceves, Randy C. (Tracy, CA)
A single-crystal, monolithic, tandem, photovoltaic solar cell is described which includes (a) an InP substrate having upper and lower surfaces, (b) a first photoactive subcell on the upper surface of the InP substrate, (c) a second photoactive subcell on the first subcell; and (d) an optically transparent prismatic cover layer over the second subcell. The first photoactive subcell is GaInAsP of defined composition. The second subcell is InP. The two subcells are lattice matched.
Wanlass, Mark W. (Golden, CO)
A single-crystal, monolithic, tandem, photovoltaic solar cell is described which includes (a) an InP substrate having upper and lower surfaces, (b) a first photoactive subcell on the upper surface of the InP substrate, (c) a second photoactive subcell on the first subcell; and (d) an optically transparent prismatic cover layer over the second subcell. The first photoactive subcell is GaInAsP of defined composition. The second subcell is InP. The two subcells are lattice matched. 9 figs.
Wanlass, M.W.
NASA Technical Reports Server (NTRS)
A front surface contact floating emitter solar cell transistor is provided in a semiconductor body (n-type), in which floating emitter sections (p-type) are diffused or implanted in the front surface. Between the emitter sections, a further section is diffused or implanted in the front surface, but isolated from the floating emitter sections, for use either as a base contact to the n-type semiconductor body, in which case the section is doped n+, or as a collector for the adjacent emitter sections.
Chih, Sah (inventor); Cheng, Li-Jen (inventor)
We present proof-of-concept all-carbon solar cells. They are made of a photoactive side of predominantly semiconducting nanotubes for photoconversion and a counter electrode made of a natural mixture of carbon nanotubes or graphite, connected by a liquid electrolyte through a redox reaction. The cells do not require rare source materials such as In or Pt, nor high-grade semiconductor processing equipment, do not rely on dye for photoconversion and therefore do not bleach, and are easy to fabricate using a spray-paint technique. We observe that cells with a lower concentration of carbon nanotubes on the active semiconducting electrode perform better than cells with a higher concentration of nanotubes. This effect is contrary to the expectation that a larger number of nanotubes would lead to more photoconversion and therefore more power generation. We attribute this to the presence of metallic nanotubes that provide a short for photo-excited electrons, bypassing the load. We demonstrate optimization strategies that improve cell efficiency by orders of magnitude. Once it is possible to make semiconducting-only carbon nanotube films, that may provide the greatest efficiency improvement. PMID:22655070
Klinger, Colin; Patel, Yogeshwari; Postma, Henk W Ch
Results from the high efficiency solar panel experiment flown on CRRES
Results from the high efficiency solar panel experiment (HESP) flown on the Combined Release and Radiation Effects Satellite (CRRES) are presented. The on-orbit solar cell degradation is correlated with the proton and electron environments. Comparisons between GaAs\\/Ge and Si solar cells are presented, and results from three different annealing methods of like GaAs solar cells are compared. Solar cell degradation
K. P. Ray; E. G. Mullen; T. M. Trumble
NASA Technical Reports Server (NTRS)
A summation of responses to questions posed to the thin-film solar cell workshop and the ensuing discussion is provided. Participants in the workshop included photovoltaic manufacturers (both thin film and crystalline), cell performance investigators, and consumers.
Armstrong, Joe; Jeffrey, Frank
Flexible solar cells for clothing
Integration of flexible solar cells into clothing can provide power for portable electronic devices. Photovoltaics is the most advanced way of providing electricity far from any mains supply, although it suffers from the limits of ambient light intensity. But the energy demand of portable devices is now low enough that clothing-integrated solar cells are able to power most mobile electronics.
Markus B. Schubert; J�rgen H. Werner
The challenges of organic polymer solar cells
The technical and commercial prospects of polymer solar cells were evaluated. Polymer solar cells are an attractive approach to fabricate and deploy roll-to-roll processed solar cells that are reasonably efficient (total ...
Saif Addin, Burhan K. (Burhan Khalid)
Commercialization of Novel Organic Solar Cells
Commercialization of Novel Organic Solar Cells Master of Engineering Final Report Shanel C. Miller ........................ 18 2.3 Novel 3D Organic Solar Cells............................................................................................................ 26 3. Manufacturing Process for 3D Organic Solar Cells
Kassegne, Samuel Kinde
GaAs Solar Cell Radiation Handbook
NASA Technical Reports Server (NTRS)
History of GaAs solar cell development is provided. Photovoltaic equations are described along with instrumentation techniques for measuring solar cells. Radiation effects in solar cells, electrical performance, and spacecraft flight data for solar cells are discussed. The space radiation environment and solar array degradation calculations are addressed.
Anspaugh, B. E.
Testing of gallium arsenide solar cells on the CRRES vehicle
NASA Technical Reports Server (NTRS)
A flight experiment was designed to determine the optimum design for gallium arsenide (GaAs) solar cell panels in a radiation environment. Elements of the experiment design include, different coverglass material and thicknesses, welded and soldered interconnects, different solar cell efficiencies, different solar cell types, and measurement of annealing properties. This experiment is scheduled to fly on the Combined Release and Radiation Effects Satellite (CRRES). This satellite will simultaneously measure the radiation environment and provide engineering data on solar cell degradation that can be directly related to radiation damage.
Trumble, T. M.
Germanium Nanocrystal Solar Cells
NASA Astrophysics Data System (ADS)
Greenhouse gas concentrations in the atmosphere are approaching historically unprecedented levels from burning fossil fuels to meet the ever-increasing world energy demand. A rapid transition to clean energy sources is necessary to avoid the potentially catastrophic consequences of global warming. The sun provides more than enough energy to power the world, and solar cells that convert sunlight to electricity are commercially available. However, the high cost and low efficiency of current solar cells prevent their widespread implementation, and grid parity is not anticipated to be reached for at least 15 years without breakthrough technologies. Semiconductor nanocrystals (NCs) show promise for cheap multi-junction photovoltaic devices. To compete with photovoltaic materials that are currently commercially available, NCs need to be inexpensively cast into dense thin films with bulk-like electrical mobilities and absorption spectra that can be tuned by altering the NC size. The Group II-VI and IV-VI NC communities have had some success in achieving this goal by drying and then chemically treating colloidal particles, but the more abundant and less toxic Group IV NCs have proven more challenging. This thesis reports thin films of plasma-synthesized Ge NCs deposited using three different techniques, and preliminary solar cells based on these films. Germanium tetrachloride is dissociated in the presence of hydrogen in a nonthermal plasma to nucleate Ge NCs. Transmission electron microscopy and X-ray diffraction indicate that the particles are nearly monodisperse (standard deviations of 10-15% the mean particle diameter) and the mean diameter can be tuned from 4-15 nm by changing the residence time of the Ge NCs in the plasma. In the first deposition scheme, a Ge NC colloid is formed by reacting nanocrystalline powder with 1-dodecene and dispersing the functionalized NCs in a solvent. Films are then formed on substrates by drop-casting the colloid and allowing it to dry. As-deposited films are electrically insulating due to the long hydrocarbon molecules separating neighboring particles; however, mass spectrometry shows that annealing treatments successfully decompose these molecules. After annealing at 250 �C, Ge NC films exhibit conductivities as large as 10-6 S/cm. In the second film deposition scheme, a Ge NC colloid is formed by dispersing Ge NCs in select solvents without further surface modification. While these "bare" NCs quickly agglomerate and flocculate in nearly all non-polar solvents, they remain stable in benzonitrile and 1,2-dichlorobenzene, among others. Thin-film field-effect transistors have been fabricated by spinning Ge NC colloids onto substrates and the films have been subjected to various annealing procedures. The devices show n-type, p -type, or ambipolar behavior depending on the annealing conditions, with Ge NC films annealed at 300�C exhibiting electron saturation mobilities greater than 10-2 cm2/Vs and on-to-off ratios of 104. The final film deposition scheme involves the impaction of Ge NCs onto substrates downstream of the synthesis plasma via acceleration of the NCs through an orifice. This technique produces highly uniform films with densities greater than 50% of the density of bulk Ge. By varying the size of the Ge NCs, we have measured films with band gaps ranging from the bulk value of 0.7 eV to over 1.1 eV for films of 4 nm Ge NCs. Having deposited dense thin films with tunable band gaps and respectable mobilities, we have begun fabricating bilayer solar cells consisting of heterojunctions between Ge NC films and P3HT, Si NCs, or Si wafers. Preliminary devices exhibit opencircuit voltages and short-circuit currents as large as 0.3 V and 4 mA/cm 2, respectively.
Holman, Zachary Charles
Solar Week: Learning from Experience
NASA Astrophysics Data System (ADS)
Solar Week is a week-long set of games and activities allowing students to interact directly with solar science and solar scientists. Solar Week was developed as a spin-off of the highly successful Yohkoh Public Outreach Project (YPOP). While YPOP provided access to solar images, movies and activities, the main goal of Solar Week was to enhance the participation of women, who are under-represented in the physical sciences. Solar Week achieves this by providing young women, primarily in grades 6-8, with access to role models in the sciences. The scientists participating in Solar Week are women from a variety of backgrounds and with a variety of scientific expertise. In this paper, our aim is to provide some insight into developing activity-based space science for the web and to discuss the lessons-learned from tailoring to a specific group of participants.
Alexander, D.; Hauck, K.
Solar-wind composition experiment
NASA Technical Reports Server (NTRS)
The Apollo program techniques for studying elemental and isotopic abundances in the solar wind are described. During Apollo 11, 12, 14 and 15 missions, aluminum foils were deployed on the lunar surface as targets for collecting solar wind ions. The foils were returned to earth, and the implanted solar wind particles were analyzed. The preliminary results showing the helium and neon concentrations are presented.
Geiss, J.; Buehler, F.; Cerutti, H.; Eberhardt, P.
Solar electron source and thermionic solar cell
NASA Astrophysics Data System (ADS)
Common solar technologies are either photovoltaic/thermophotovoltaic, or use indirect methods of electricity generation such as boiling water for a steam turbine. Thermionic energy conversion based on the emission of electrons from a hot cathode into vacuum and their collection by an anode is also a promising route. However, thermionic solar conversion is extremely challenging as the sunlight intensity is too low for heating a conventional cathode to thermionic emission temperatures in a practical manner. Therefore, compared to other technologies, little has been done in this area, and the devices have been mainly limited to large experimental apparatus investigated for space power applications. Based on a recently observed "Heat Trap" effect in carbon nanotube arrays, allowing their efficient heating with low-power light, we report the first compact thermionic solar cell. Even using a simple off-the-shelf focusing lens, the device delivered over 1 V across a load. The device also shows intrinsic storage capacity.
Yaghoobi, Parham; Vahdani Moghaddam, Mehran; Nojeh, Alireza
Module level solutions to solar cell polarization
A solar cell module includes interconnected solar cells, a transparent cover over the front sides of the solar cells, and a backsheet on the backsides of the solar cells. The solar cell module includes an electrical insulator between the transparent cover and the front sides of the solar cells. An encapsulant protectively packages the solar cells. To prevent polarization, the insulator has resistance suitable to prevent charge from leaking from the front sides of the solar cells to other portions of the solar cell module by way of the transparent cover. The insulator may be attached (e.g., by coating) directly on an underside of the transparent cover or be a separate layer formed between layers of the encapsulant. The solar cells may be back junction solar cells.
Xavier, Grace (Fremont, CA), Li; Bo (San Jose, CA)
NASA Technical Reports Server (NTRS)
The Space Plasma, High Voltage Interaction Experiment (SPHINX) is the name given to an auxiliary payload satellite scheduled to be launched in January 1974. The principal experiments carried on this satellite are specifically designed to obtain the engineering data on the interaction of high voltage systems with the space plasma. The classes of experiments are solar array segments, insulators, insulators with pin holes and conductors. The satellite is also carrying experiments to obtain flight data on three new solar array configurations: the edge illuminated-multijunction cells, the teflon encased cells, and the violet cells.
Stevens, N. J.
On solar neutrino fluxes in radiochemical experiments
We analyze fluctuations of the solar neutrino flux using data from the Homestake, GALLEX, GNO, SAGE and Super Kamiokande experiments. Spectral analysis and direct quantitative estimations show that the most stable variation of the solar neutrino flux is a quasi-five-year periodicity. The revised values of the mean solar neutrino flux are presented in Table 4. They were used to estimate the observed pp-flux of the solar electron neutrinos near the Earth. We consider two alternative explanations for the origin of a variable component of the solar neutrino deficit.
R. N. Ikhsanov; Yu. N. Gnedin; E. V. Miletsky
Solar cell with back side contacts
A III-V solar cell is described herein that includes all back side contacts. Additionally, the positive and negative electrical contacts contact compoud semiconductor layers of the solar cell other than the absorbing layer of the solar cell. That is, the positive and negative electrical contacts contact passivating layers of the solar cell.
Nielson, Gregory N; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J; Wanlass, Mark Woodbury; Clews, Peggy J
EE580 Solar Cells Todd J. Kaiser
7/21/2010 1 EE580 Solar Cells Todd J. Kaiser · Lecture 10 · Summary 1Montana State University: Solar Cells Lecture 10: Summary Summer 2010 Class Montana State University: Solar Cells Lecture 10: Summary 2 Solar Cell Operation n Emitter p Base Rear Contact Antireflection coating Absorption of photon
Kaiser, Todd J.
CCMR: Nanocrystal Sensitized Solar Cells
NSDL National Science Digital Library
Nanocrystal sensitized solar cells demonstrate a possible cheap solution to practical device manufacture. This research examined the feasibility of using lead sulfide nanocrystals to sensitize tin dioxide and titanium dioxide substrates for the purpose of making a functioning photovoltaic device. Challenges included optimizing the substrate materials as well as the thin films made from them. Results indicate that titanium dioxide produces more suitable thin films than tin dioxide. Also, the methods employed did produce a functioning solar cell after optimization.
Perry, Alexis
NASA Technical Reports Server (NTRS)
A solar panel cleaning device includes a solar panel having a plurality of photovoltaic cells arranged in rows and embedded in the solar panel with space between the rows. A transparent dielectric overlay is affixed to the solar panel. A plurality of electrode pairs each of which includes an upper and a lower electrode are arranged on opposite sides of the transparent dielectric and are affixed thereto. The electrodes may be transparent electrodes which may be arranged without concern for blocking sunlight to the solar panel. The solar panel may be a dielectric and its dielectric properties may be continuously and spatially variable. Alternatively the dielectric used may have dielectric segments which produce different electrical field and which affects the wind "generated."
Ashpis, David E. (Inventor)
June 2009 UWMREPORT 15 solar cells turn Bolton roof
's late- afternoon demand can be met by the energy from the solar panels. Lab members also will experimentJune 2009 · UWMREPORT · 15 solar cells turn Bolton roof into an energy lab By Laura L. Hunt hanks are behind the acquisition of 74 solar panels that were recently installed on the second-floor roof of Bolton
Saldin, Dilano
NASA Astrophysics Data System (ADS)
Thin-film solar cells with a Cu-based chalcopyrite absorber achieve high conversion efficiencies (up to 20%). Their technology being more cost effective than the crystalline silicon technologies, they are expected to replace Si-based solar cells. But a best cost-performance ratio requires first a knowledge of the parameters which ascertain the electrical quality of the solar cell. The first of them is the minority carrier diffusion length in the absorber and the second one is the collection efficiency of the p-n junction space charge region (SCR) located within the absorber. A low value of at least one of them drastically reduces the efficiency of the cell. In this paper we present an electron-beam-induced-current (EBIC) determination of these two parameters in CIS solar cells.
Sieber, B.; Ruiz, C. M.; Bermudez, V.
The solar molten salt electric experiment
The solar Molten Salt Electric Experiment (MSEE) is now in operation at the Central Receiver Test Facility (CRTF) near Albuquerque, NM. The MSEE uses a molten salt as its solar receiver and thermal storage working fluid and uses water\\/steam as its electric power generating fluid. The molten sodium nitrate (60 percent) and potassium nitrate (40 percent) salt melts at about
Space solar cells�tradeoff analysis
This paper summarizes the study that had the objective to tradeoff space solar cells and solar array designs to determine the best choice of solar cell and array technology that would be more beneficial in terms of mass, area and cost for different types of space missions. Space solar cells, which are commercially now available in the market and to
M. Raja Reddy
An improved transparent conductor structure for thin film solar cells comprising a plurality of metallic strip conductors deposited on a transparent conductor and aligned substantially with the principal direction of current flow. The strip conductors preferably originate at an edge of the transparent conductor to which an adjacent cell back conductor is connected and are preferably interconnected along that edge
D. P. Tanner; R. R. Gay; D. L. Morel
Interdigitated back contact solar cells
NASA Astrophysics Data System (ADS)
The interdigitated back contact solar cell (IBC cell) was shown to possess a number of advantages for silicon solar cells, which operate at high concentration. A detailed discussion of the factors which need to be considered in the analysis of semiconducting devices which utilize heavily doped regions such as those which are found in solar cells in both the emitter and in the back surface field regions is given. This discussion covers the questions of: how to handle degeneracy, how to compute carrier concentrations in the absence of knowledge of the details of the band structure under heavily doped conditions, and how to reconcile the usual interpretation of heavy doping as a rigid shift of the bands with the band tailing and impurity level conduction models. It also discusses the reasons for the observed discrepancies between various experimental measurements of bandgap narrowing.
Lundstrom, M. S.; Schwartz, R. J.
Organic Semiconductor Solar Cells
NASA Astrophysics Data System (ADS)
Several aspects of organic photoconductors investigated for photovoltaic (PV) applications are addressed: material selection criteria, device modelling, and the characterization techniques of I-V, capacitance-voltage (C-V), I _{sc} vs. V_{oc }, and internal photoemission. Experimental results are presented for chloroaluminum phthalocyanine (ClAlPc) Schottky barrier and p-n heterojunction cells. The principal limitation of organic PV materials is a low field-dependent photocarrier generation efficiency. P -n heterojunction cells have advantages over Schottky cells, having better spectral coverage and the ability to utilize Forster transfer for the transport and concentration of excitons to a high field region. A promising approach pairs a phthalocyanine and a perylene. A simpler Schottky barrier system is modelled using parameters for the field -dependent generation of metal-free phthalocyanine. The effects of doping level, alpha, and other parameters on the external cell characteristics are calculated based on the electric field in the depletion region. Although this modelling does not include the effects of exciton diffusion, the wavelength dependence of the external quantum efficiency mimics results thought to indicate an exciton diffusion process. The device fabrication procedure utilizes vacuum deposition of organic semiconductors purified by entrainment sublimation. Films deposited at different substrate temperatures are characterized with optical absorption, x-ray, and scanning electron microscopy. A hydration mechanism for ClAlPc is uncovered, and powder x-ray results are presented. The photoresponses for a perylene derivative paired with ClAlPc and PcAlOAlPc are presented. The C-V spectroscopy methods are reviewed, and the small signal method is argued to be preferable to the triangle voltage sweep method due to the likely presence of deep traps and interface states. C -V results are shown to bias hold-time dependent so that straight 1/C^2 vs. V plots should be interpreted with caution. Experiments under vacuum, air, dry oxygen, water vapor, and oxygen with water vapor ambients show water and oxygen are necessary for the ClAlPc to exhibit significant conductivity and C-V response. This suggests that water and oxygen must both be present for significant doping effects.
Whitlock, Jonathan B.
Gap/silicon Tandem Solar Cell with Extended Temperature Range
NASA Technical Reports Server (NTRS)
A two-junction solar cell has a bottom solar cell junction of crystalline silicon, and a top solar cell junction of gallium phosphide. A three (or more) junction solar cell has bottom solar cell junctions of silicon, and a top solar cell junction of gallium phosphide. The resulting solar cells exhibit improved extended temperature operation.
Landis, Geoffrey A. (Inventor)
Solar exposure of LDEF experiment trays
NASA Technical Reports Server (NTRS)
Exposure to solar radiation is one of the primary causes of degradation of materials on spacecraft. Accurate knowledge of solar exposure is needed to evaluate the performance of materials carried on the Long Duration Exposure Facility (LDEF) during its nearly 6 year orbital flight. Presented here are tables and figures of calculated solar exposure for the experiment rows, longerons, and end bays of the spacecraft as functions of time in orbit. The data covers both direct solar and earth reflected radiation. Results are expressed in cumulative equivalent sun hours (CESH) or the hours of direct, zero incidence solar radiation that would cause the same irradiance of a surface. Space end bays received the most solar radiation, 14,000 CESH; earth end bays received the least, 4,500 CESH. Row locations received between 6,400 CESH and 11,200 CESH with rows facing either eastward or westward receiving the most radiation and rows facing northward or southward receiving the least.
Bourassa, R. J.; Gillis, J. R.
Solar exposure of LDEF experiment trays
Exposure to solar radiation is one of the primary causes of degradation of materials on spacecraft. Accurate knowledge of solar exposure is needed to evaluate the performance of materials carried on the Long Duration Exposure Facility (LDEF) during its nearly 6 year orbital flight. Presented here are tables and figures of calculated solar exposure for the experiment rows, longerons, and end bays of the spacecraft as functions of time in orbit. The data covers both direct solar and earth reflected radiation. Results are expressed in cumulative equivalent sun hours (CESH) or the hours of direct, zero incidence solar radiation that would cause the same irradiance of a surface. Space end bays received the most solar radiation, 14,000 CESH; earth end bays received the least, 4,500 CESH. Row locations received between 6,400 CESH and 11,200 CESH with rows facing either eastward or westward receiving the most radiation and rows facing northward or southward receiving the least.
Bourassa, R.J.; Gillis, J.R.
High voltage solar array experiments
NASA Technical Reports Server (NTRS)
The interaction between the components of a high voltage solar array and a simulated space plasma is studied to obtain data for the design of a high voltage solar array capable of 15kW at 2 to 16kV. Testing was conducted in a vacuum chamber 1.5-m long by 1.5-m diameter having a plasma source which simulated the plasma conditions existing in earth orbit between 400 nautical miles and synchronous altitude. Test samples included solar array segments pinholes in insulation covering high voltage electrodes, and plain dielectric samples. Quantitative data are presented in the areas of plasma power losses, plasma and high voltage induced damage, and dielectric properties. Limitations of the investigation are described.
Kennerud, K. L.
Quantum dot sensitized solar cells
Metal sulfide (CdS or PbS) quantum dots were synthesized in nanoporous TiO2 films for applications in solar energy conversion devices. Several electrolytes were investigated for the functioning redox activity in sandwich type regenerative solar cells, based on the quantum dots sensitized TiO2 film. A high IPCE was attained by optimizing the polysulfide electrolyte composition. The CdS QD shows a higher
Y. Tachibana; H. Y. Akiyama; K. Umekita; Y. Otsuka; T. Torimoto; S. Kuwabata
The Galileo solar redshift experiment
NASA Technical Reports Server (NTRS)
From the October 1989 launch to the first December 1990 earth gravity assist, we regularly obtained frequency measurements of the spacecraft clock - an ultrastable crystal oscillator (USO) supplied by Frequency Electronics, Inc. The solar gravitational redshift in frequency was readily detectable, and because of the unique variations in heliocentric distance we could separate the general relativistic effects from the USO's intrinsic frequency variations. We have verified the total frequency shift predicted by general relativity to 0.5 percent accuracy, and the solar gravitational redshift to 1 percent accuracy.
Krisher, Timothy P.; Morabito, David D.; Anderson, John D.
Summary of solar cell data from the Long Duration Exposure Facility (LDEF)
NASA Technical Reports Server (NTRS)
The Long Duration Exposure Facility (LDEF) was composed of many separate experiments, some of which contained solar cells. These solar cells were distributed at various positions on the LDEF and, therefore, were exposed to the space environment with an orientational dependence. This report will address the space environmental effects on solar cells and solar cell assemblies (SCA's), including electrical interconnects and associated insulation blankets where flown in conjunction with solar cells.
Hill, David C.; Rose, M. Frank
Efficiencies of more than 33% have been achieved today in the photovoltaic conversion of solar energy into electricity. Part of this achievement is due to a effective coupling of sunlight to the solar cell. In particular three aspects of light-cell coupling are studied here: (a) the achievement of high irradiance on the cell; that is, the study of concentration; (b) the increase of the absorption in the cell and (c) the matching of the sun spectrum to the cell, with the use of several cells or thermo-photovoltaic devices. Finally, the ultimate limits of the efficiency of solar cells, and photovoltaic devices in general, are studied. It is found that efficiencies in the range of 85% (depending on the spectrum of the sun) are theoretically possible. Also the conditions for thermodynamically reversible operation are analyzed. Some laboratory results are presented and the role of the light-cell coupling in the achievement of this high efficiency is stressed. 70 refs., 30 figs., 6 tabs.
Luque, A. [Univ. Polytecnica de Madrid (Spain). Inst. de Energia Solar; [Ciudad Univ., Madrid (Spain). E.T.S.I. Telecomunicacion
Solar Energy Experiment for Beginning Chemistry.
ERIC Educational Resources Information Center
Describes an experiment illustrating how such chemical concepts as light absorption, thermodynamics, and solid-state photovoltaics can be incorporated into solar energy education. Completed in a three-hour period, the experiment requires about two hours for data collections with the remaining hour devoted to calculations and comparison of results.�
Davis, Clyde E.
Solar Radiation and Climate Experiment (SORCE) Satellite
NASA Technical Reports Server (NTRS)
This is a close-up of the NASA-sponsored Solar Radiation and Climate Experiment (SORCE) Satellite. The SORCE mission, launched aboard a Pegasus rocket January 25, 2003, will provide state of the art measurements of incoming x-ray, ultraviolet, visible, near-infrared, and total solar radiation. Critical to studies of the Sun and its effect on our Earth system and mankind, SORCE will provide measurements that specifically address long-term climate change, natural variability and enhanced climate prediction, and atmospheric ozone and UV-B radiation. Orbiting around the Earth accumulating solar data, SORCE measures the Sun's output with the use of state-of-the-art radiometers, spectrometers, photodiodes, detectors, and bolo meters engineered into instruments mounted on a satellite observatory. SORCE is carrying 4 instruments: The Total Irradiance Monitor (TIM); the Solar Stellar Irradiance Comparison Experiment (SOLSTICE); the Spectral Irradiance Monitor (SIM); and the XUV Photometer System (XPS).
Performance of silicon solar cell assemblies
NASA Technical Reports Server (NTRS)
Solar cell assembly current-voltage characteristics, thermal-optical properties, and power performance were determined. Solar cell cover glass thermal radiation, optical properties, confidence limits, and temperature intensity effects on maximum power were discussed.
Ross, R. G., Jr.; Yasui, R. K.; Jaworski, W.; Wen, L.; Cleland, E. L.
Solar Mass Ejection Imager (SMEI) space experiment
The Solar Mass Ejection Imager (SMEI) is a proof-of-concept space experiment designed to observe solar coronal mass ejections (CMEs) and forecast their arrival at Earth. SMEI will image CMEs by sensing sunlight scattered from the free electrons in these ejecta (i.e., Thomson scattering). SMEI will be launched by a Titan II rocket into a circular, 830-km, sun-synchronous orbit in mid-2002
Richard R. Radick
Solar power tower development: Recent experiences
Recent experiences with the 10 MW{sub e} Solar Two and the 2.5 MW{sub t} TSA (Technology Program Solar Air Receiver) demonstration plants are reported. The heat transfer fluids used in these solar power towers are molten-nitrate salt and atmospheric air, respectively. Lessons learned and suggested technology improvements for next-generation plants are categorized according to subsystem. The next steps to be taken in the commercialization process for each these new power plant technologies is also presented.
Tyner, C.; Kolb, G.; Prairie, M. [and others
NASA Technical Reports Server (NTRS)
Limitations in both space and terrestial markets for solar cells are described. Based on knowledge of the state-of-the-art, six cell options are discussed; as a result of this discussion, the three most promising options (involving high, medium and low efficiency cells respectively) were selected and analyzed for their probable costs. The results showed that all three cell options gave promise of costs below $10 per watt in the near future. Before further cost reductions can be achieved, more R and D work is required; suggestions for suitable programs are given.
Iles, P. A.; Mclennan, H.
Multicrystalline silicon bifacial solar cells
The authors analyze the results of several batches of multicrystalline silicon bifacial solar cells (HEM and cast). They measured the I-V curves under front and back illuminations and also in the dark. In the last case they carried out measurements at several temperatures. It was concluded that HEM wafers might be used to manufacture commercial bifacial cells, while the high base recombination prevents the use of cast wafers for this purpose.
Jimeno, J.C.; Luque, A.
Key Physical Mechanisms in Nanostructured Solar Cells
The objective of the project was to study both theoretically and experimentally the excitation, recombination and transport properties required for nanostructured solar cells to deliver energy conversion efficiencies well in excess of conventional limits. These objectives were met by concentrating on three key areas, namely, investigation of physical mechanisms present in nanostructured solar cells, characterization of loss mechanisms in nanostructured solar cells and determining the properties required of nanostructured solar cells in order to achieve high efficiency and the design implications.
Dr Stephan Bremner
Nature's Kitchen: Solar Box Cooker Experiment
NSDL National Science Digital Library
The Materials Science and Technology Teacher's Workshop (MAST) provides this activity to support solar energy curriculum. The goal of the experiment is to allow students to create a device to cook food with energy from the sun. The experiment teaches the procedures to build a solar cooker to use if trapped without a cooking stove while camping. The introduction is very basic and the instructor can opt to build the solar cooker beforehand to save class time. In the end, several cookers will be built, and their degree of cooking effectiveness is monitored through several small pieces of potatoes cooked over several hours.The lesson includes step by step directions for the experiment. Discussion questions and teacher notes are also included.
EE580 Solar Cells Todd J. Kaiser
7/21/2010 1 EE580 Solar Cells Todd J. Kaiser · Lecture 02 Microfabrication A combination · Photolithograpy · Depostion · Etching 1 Montana State University: Solar Cells Lecture 2: Microfabrication Flow Montana State University: Solar Cells Lecture 2: Microfabrication Questions · What is heat? · Heat
Kaiser, Todd J.
Nanostructured Materials for Solar Cells
NASA Technical Reports Server (NTRS)
The use of both inorganic and organic nanostructured materials in producing high efficiency photovoltaics is discussed in this paper. Recent theoretical results indicate that dramatic improvements in device efficiency may be attainable through the use of semiconductor quantum dots in an ordinary p-i-n solar cell. In addition, it has also recently been demonstrated that quantum dots can also be used to improve conversion efficiencies in polymeric thin film solar cells. A similar improvement in these types of cells has also been observed by employing single wall carbon nanotubes. This relatively new carbon allotrope may assist both in the disassociation of excitons as well as carrier transport through the composite material. This paper reviews the efforts that are currently underway to produce and characterize these nanoscale materials and to exploit their unique properties.
Bailey, Sheila; Raffaelle, Ryne; Castro, Stephanie; Fahey, S.; Gennett, T.; Tin, P.
Photoelectrochemical cells using dye-sensitized ZnO with a Cu2+\\/Fe2+\\/Fe3+ electrolyte can be easily made at home or in a school classroom with household chemicals and other readily available materials. The cells, which are made with wire housed within plastic drinking straws, have open-circuit voltages of 0.5-0.7 V and short-circuit currents of about 0.5-2.5 mA cm-2. Step-by-step instructions are provided on how
S. J. Appleyard
Photoelectrochemical cells using dye-sensitized ZnO with a Cu2+\\/Fe2+\\/Fe3+ electrolyte can be easily made at home or in a school classroom with household chemicals and other readily available materials. The cells, which are made with wire housed within plastic drinking straws, have open-circuit voltages of 0.5�0.7 V and short-circuit currents of about 0.5�2.5 mA cm?2. Step-by-step instructions are provided on how
S J Appleyard
Cascade Solar Cell Workshop report
NASA Technical Reports Server (NTRS)
Issues related to the feasibility, research and development, and demonstration of a 30% AMO cascade solar cell discussed include the material selection, growth and fabrication techniques, and device development strategy for a monolithic (two terminal) cascade cell, a hybrid (four terminal) cascade cell, and a spectral splitting device (three cells). Workshop recommendations include: (1) initiate a long range research program to develop a three junction, monolithic, cascade cell using either AlGaAsSb-GaAsSb or AlGaInAs-GaInAs material system; (2) emphasize OM-CVD epitaxial growth technique, perhaps combined with other technologies in the near term to obtain tunnel junctions; (3) develop a two junction device first; (4) initiate a cascade solar cell modeling program to study and compare performance of two and four terminal cascade devices exposed to electron and proton irradiation; and (5) encourage and be open to new ideas for developing four terminal, hybrid, cascade cells exploiting novel component cell interconnect technologies.
Hutchby, J. A.
Recent reports have demonstrated the possibility of employing photoactive, biological membrane components in photoelectrochemical cells. Present studies in our laboratories have led to the attachment of a much simpler biological complex, the bacterial photosynthetic reaction center isolated from Rhodopseudomonas sphaeroides, directly onto a SnO/sub 2/ semiconductor electrode. Light-induced photovoltages (70mV) and photocurrents (0.5 ..mu..A/cm/sup 2/) not attributable to Dember effects have been observed in photoelectrochemical cells employing reaction-center-coated, SnO/sub 2/ working electrodes. Such reaction-center electrodes may serve as model systems for future organic photovoltaic devices.
Seibert, M.; Janzen, A.F.
Mixed ternary heterojunction solar cell
A thin film heterojunction solar cell and a method of making it has a p-type layer of mixed ternary I-III-VI.sub.2 semiconductor material in contact with an n-type layer of mixed binary II-VI semiconductor material. The p-type semiconductor material includes a low resistivity copper-rich region adjacent the back metal contact of the cell and a composition gradient providing a minority carrier mirror that improves the photovoltaic performance of the cell. The p-type semiconductor material preferably is CuInGaSe.sub.2 or CuIn(SSe).sub.2.
Chen, Wen S. (Seattle, WA); Stewart, John M. (Seattle, WA)
Flexibility in space solar cell production
NASA Technical Reports Server (NTRS)
The wide range of cells that must be available from present-day production lines for space solar cells are described. After over thirty years of space-cell use, there is very little standardization in solar cell design. It is not generally recognized what a wide range of designs must remain available on cell production lines. This range of designs is surveyed.
Khemthong, Scott; Iles, Peter A.
Towards stable silicon nanoarray hybrid solar cells
Silicon nanoarray hybrid solar cells benefit from the ease of fabrication and the cost-effectiveness of the hybrid structure, and represent a new research focus towards the utilization of solar energy. However, hybrid solar cells composed of both inorganic and organic components suffer from the notorious stability issue, which has to be tackled before the hybrid solar cells could become a viable alternative for harvesting solar energy. Here we show that Si nanoarray/PEDOT:PSS hybrid solar cells with improved stability can be fabricated via eliminating the water inclusion in the initial formation of the heterojunction between Si nanoarray and PEDOT:PSS. The Si nanoarray hybrid solar cells are stable against rapid degradation in the atmosphere environment for several months without encapsulation. This finding paves the way towards the real-world applications of Si nanoarray hybrid solar cells. PMID:24430057
He, W. W.; Wu, K. J.; Wang, K.; Shi, T. F.; Wu, L.; Li, S. X.; Teng, D. Y.; Ye, C. H.
GaAs Solar Cell Radiation Handbook
NASA Technical Reports Server (NTRS)
The handbook discusses the history of GaAs solar cell development, presents equations useful for working with GaAs solar cells, describes commonly used instrumentation techniques for assessing radiation effects in solar cells and fundamental processes occurring in solar cells exposed to ionizing radiation, and explains why radiation decreases the electrical performance of solar cells. Three basic elements required to perform solar array degradation calculations: degradation data for GaAs solar cells after irradiation with 1 MeV electrons at normal incidence; relative damage coefficients for omnidirectional electron and proton exposure; and the definition of the space radiation environment for the orbit of interest, are developed and used to perform a solar array degradation calculation.
Anspaugh, B. E.
24% efficient silicon solar cells
This paper reports significant progress in silicon solar cell performance, taking confirmed efficiency beyond 24% for the first time. This progress has been achieved by a combination of several mechanisms. One is the reduction of recombination at the cell front surface by improved passivation of the silicon/silicon dioxide interface. Resistive losses in the cell have been reduced by a double-plating process which increases the thickness for the coarse cell metallization features. Finally, reflective losses have been reduced by the application of a double layer anti-reflection (DLAR) coating. Another advantage of DLAR coating is that it will give further 3% higher current density than the SiO{sub 2} single layer anti-reflection (SLAR) coated cells when encapsulated into modules. The cells display a monochromatic light energy conversion efficiency of 46.3% for 1.04 {micro}m wavelength light, also the highest ever for a silicon device.
Zhao, J.; Wang, A.; Altermatt, P.P.; Wenham, S.R.; Green, M.A. [Univ. of New South Wales, Sydney, New South Wales (Australia). Centre for Photovoltaic Devices and Systems
High efficiency GaAs solar cells
NASA Technical Reports Server (NTRS)
The present status of the GaAlAs/GaAs heteroface solar cell program is reported. Studies have been concentrated on GaAlAs/GaAs heteroface solar cells; however, some research has been conducted on thin junction, diffused GaAs solar cells. Emphasis has been on obtaining high efficiency (18% to 20%) GaAs solar cells. Two problems that have limited the efficiency of GaAs solar cells are the high recombination velocity of carriers near the surface and the low minority carrier diffusion length in n-GaAs.
Walker, G. H.; Conway, E. J.; Byvik, C. E.
Solar Irradiance and Thermospheric Airglow Rocket Experiments
NASA Technical Reports Server (NTRS)
This report describes work done in support of the Solar Irradiance and Thermospheric Air-glow Rocket Experiments at the University of Colorado for NASA grant NAG5-5021 under the direction of Dr. Stanley C. Solomon. (The overall rocket program is directed by Dr. Thomas N. Woods, formerly at the National Center for Atmospheric Research, and now also at the University of Colorado, for NASA grant NAG5-5141.) Grant NAG5-5021 provided assistance to the overall program through analysis of airglow and solar data, support of two graduate students, laboratory technical services, and field support. The general goals of the rocket program were to measure the solar extreme ultraviolet spectral irradiance, measure the terrestrial far-ultraviolet airglow, and analyze their relationship at various levels of solar activity, including near solar minimum. These have been met, as shown below. In addition, we have used the attenuation of solar radiation as the rocket descends through the thermosphere to measure density changes. This work demonstrates the maturity of the observational and modeling methods connecting energetic solar photon fluxes and airglow emissions through the processes of photoionization and photoelectron production and loss. Without a simultaneous photoelectron measurement, some aspects of this relationship remain obscure, and there are still questions pertaining to cascade contributions to molecular and atomic airglow emissions. However, by removing the solar irradiance as an "adjustable parameter" in the analysis, significant progress has been made toward understanding the relationship of far-ultraviolet airglow emissions to the solar and atmospheric conditions that control them.
Solomon, Stanley C.
Organic Semiconductor Solar Cells
Several aspects of organic photoconductors investigated for photovoltaic (PV) applications are addressed: material selection criteria, device modelling, and the characterization techniques of I-V, capacitance-voltage (C-V), I _{sc} vs. V_{oc }, and internal photoemission. Experimental results are presented for chloroaluminum phthalocyanine (ClAlPc) Schottky barrier and p-n heterojunction cells. The principal limitation of organic PV materials is a low field-dependent photocarrier generation
Jonathan B. Whitlock
Arcing of negatively biased solar cells in a plasma environment
Experimental and theoretical efforts have been conducted to investigate the arcing of negatively biased solar arrays in a low-Earth orbit plasma environment. Experiments were conducted in an ultrahigh vacuum plasma test chamber, where the environment could be controlled carefully. Outgassing of the adhesive used to bind the protective coverglass to the solar cells was determined to be a key factor
B. L. Upschulte; W. J. Marinelli; K. L. Carleton; G. Weyl; E. Aifer; D. E. Hastings
Solar axion search with the CAST experiment
The CAST (CERN Axion Solar Telescope) experiment is searching for solar axions by their conversion into photons inside the magnet pipe of an LHC dipole. The analysis of the data recorded during the first phase of the experiment with vacuum in the magnet pipes has resulted in the most restrictive experimental limit on the coupling constant of axions to photons. In the second phase, CAST is operating with a buffer gas inside the magnet pipes in order to extent the sensitivity of the experiment to higher axion masses. We will present the first results on the $^{4}{\\rm He}$ data taking as well as the system upgrades that have been operated in the last year in order to adapt the experiment for the $^{3}{\\rm He}$ data taking. Expected sensitivities on the coupling constant of axions to photons will be given for the recent $^{3}{\\rm He}$ run just started in March 2008.
CAST Collaboration; E. Arik; S. Aune; D. Autiero; K. Barth; A. Belov; B. Beltr�n; S. Borghi; F. S. Boydag; H. Br�uninger; G. Cantatore; J. M. Carmona; S. A. Cetin; J. I. Collar; T. Dafni; M. Davenport; L. Di Lella; O. B. Dogan; C. Eleftheriadis; N. Elias; G. Fanourakis; E. Ferrer-Ribas; H. Fischer; J. Franz; J. Gal�n; E. Gazis; T. Geralis; I. Giomataris; S. Gninenko; H. G�mez; M. Hasinoff; F. H. Heinsius; I. Hikmet; D. H. H. Hoffmann; I. G. Irastorza; J. Jacoby; K. Jakov?i?; D. Kang; T. Karageorgopoulou; M. Karuza; K. K�nigsmann; R. Kotthaus; M. Kr?mar; K. Kousouris; M. Kuster; B. Laki?; C. Lasseur; A. Liolios; A. Ljubi?i?; V. Lozza; G. Lutz; G. Luz�n; D. Miller; J. Morales; T. Niinikoski; A. Nordt; A. Ortiz; T. Papaevangelou; M. J. Pivovaroff; A. Placci; G. Raiteri; G. Raffelt; H. Riege; A. Rodr�guez; J. Ruz; I. Savvidis; Y. Semertzidis; P. Serpico; S. K. Solanki; R. Soufli; L. Stewart; M. Tsagri; K. van Bibber; J5D. Villar; J. Vogel; L. Walckiers; K. Zioutas
TIMED Solar EUV Experiment: Phase E
NASA Technical Reports Server (NTRS)
The timed Solar EUV Experiment (SEE) Phase E Annual Report for 2002 is presented. The contents include: 1) SEE Science Overview; 2) SEE Instrument Overview and Status; 3) Summary of SEE Data Products; 4) Summary of SEE Results; 5) Summary of SEE Related Talks and Papers; and 6) Future Plans for SEE Team. This paper is in viewgraph form.
Woods, Tom; Eparvier, Frank; Woodraska, Don; Rottman, Gary; Solomon, Stan; Roble, Ray; deToma, Guliana; White, Dick; Lean, Judith; Tobiska, Kent; Bailey, Scott
TIMED Solar EUV Experiment: Phase E.
National Technical Information Service (NTIS)
The timed Solar EUV Experiment (SEE) Phase E Annual Report for 2002 is presented. The contents include: 1) SEE Science Overview; 2) SEE Instrument Overview and Status; 3) Summary of SEE Data Products; 4) Summary of SEE Results; 5) Summary of SEE Related T...
T. Woods, F. Eparvier, D. Woodraska, G. Rottman, S. Solomon, R. Roble, G. deToma, D. White, J. Lean, K. Tobiska, S. Bailey
Solar Cells, 3 (1981) 337 -340 337 HIGH EFFICIENCY BIFACIAL BACK SURFACE FIELD SOLAR CELLS
. CUEVAS, A. LUQUE, J. EGUREN and J. DEL ALAMO Instituto de Energia Solar, Escuela Tdcnica Superior deSolar Cells, 3 (1981) 337 - 340 337 HIGH EFFICIENCY BIFACIAL BACK SURFACE FIELD SOLAR CELLS A solar cells are presented. Effi- ciencies of 15.7% and 13.6% were measured under front and back air mass
del Alamo, Jesús A.
First-principles computer simulations can contribute to a deeper understanding of the dye/semiconductor interface lying at the heart of Dye-sensitized Solar Cells (DSCs). Here, we present the results of simulation of dye adsorption onto TiO(2) surfaces, and of their implications for the functioning of the corresponding solar cells. We propose an integrated strategy which combines FT-IR measurements with DFT calculations to individuate the energetically favorable TiO(2) adsorption mode of acetic acid, as a meaningful model for realistic organic dyes. Although we found a sizable variability in the relative stability of the considered adsorption modes with the model system and the method, a bridged bidentate structure was found to closely match the FT-IR frequency pattern, also being calculated as the most stable adsorption mode by calculations in solution. This adsorption mode was found to be the most stable binding also for realistic organic dyes bearing cyanoacrylic anchoring groups, while for a rhodanine-3-acetic acid anchoring group, an undissociated monodentate adsorption mode was found to be of comparable stability. The structural differences induced by the different anchoring groups were related to the different electron injection/recombination with oxidized dye properties which were experimentally assessed for the two classes of dyes. A stronger coupling and a possibly faster electron injection were also calculated for the bridged bidentate mode. We then investigated the adsorption mode and I(2) binding of prototype organic dyes. Car-Parrinello molecular dynamics and geometry optimizations were performed for two coumarin dyes differing by the length of the ?-bridge separating the donor and acceptor moieties. We related the decreasing distance of the carbonylic oxygen from the titania to an increased I(2) concentration in proximity of the oxide surface, which might account for the different observed photovoltaic performances. The interplay between theory/simulation and experiments appears to be the key to further DSCs progress, both concerning the design of new dye sensitizers and their interaction with the semiconductor and with the solution environment and/or an electrolyte upon adsorption onto the semiconductor. PMID:23108504
Anselmi, Chiara; Mosconi, Edoardo; Pastore, Mariachiara; Ronca, Enrico; De Angelis, Filippo
NASA Technical Reports Server (NTRS)
The thermal imaging technique was evaluated for its capabilities in the nondestructive evaluation of solar cell welds. The temperature and spatial resolution of state of the art instrumentation was sufficient for both qualitative and quantitative determination of the quality of solar cell welds. The addition of color digitized thermography enhanced the aspects of the thermographic display and allowed easily computerized testing procedures. For automated testing systems an accurate correlation of weld quality with temperature profiles of the welds needs to be performed. In comparison, the holographic technique was complementary with the thermal imaging technique, except that the holographic analysis appeared to be more quantitative at the present time. However, the thermal imaging approach is much more versatile in overall capabilities.
Workman, G. L.
High Temperature Solar Cell Development
NASA Technical Reports Server (NTRS)
The majority of satellites and near-earth probes developed to date have used photovoltaic arrays for power generation. If future mission to probe environments close to the sun will be able to use photovoltaic power, solar cells that can function at high temperatures, under high light intensity, and high radiation conditions must be developed. In this paper, we derive the optimum bandgap as a function of the operating temperature.
Landis, Geoffrey A.; Raffaelle, Ryne P.; Merritt, Danielle
EE580 Solar Cells Todd J. Kaiser
Lecture 9: PV Systems Specifications of PV Modules · Type c:Si, a-Si:H, CdTe · Rated Power Max: Pmax (Wp Cells loose efficiency with the increase in temperature Colder is better Solar Heating Montana State University: Solar Cells Lecture 9: PV Systems 11 Solar heating (70-90%) is more efficient than photovoltaic
Kaiser, Todd J.
Silicon Carbide Solar Cells Investigated
NASA Technical Reports Server (NTRS)
The semiconductor silicon carbide (SiC) has long been known for its outstanding resistance to harsh environments (e.g., thermal stability, radiation resistance, and dielectric strength). However, the ability to produce device-quality material is severely limited by the inherent crystalline defects associated with this material and their associated electronic effects. Much progress has been made recently in the understanding and control of these defects and in the improved processing of this material. Because of this work, it may be possible to produce SiC-based solar cells for environments with high temperatures, light intensities, and radiation, such as those experienced by solar probes. Electronics and sensors based on SiC can operate in hostile environments where conventional silicon-based electronics (limited to 350 C) cannot function. Development of this material will enable large performance enhancements and size reductions for a wide variety of systems--such as high-frequency devices, high-power devices, microwave switching devices, and high-temperature electronics. These applications would supply more energy-efficient public electric power distribution and electric vehicles, more powerful microwave electronics for radar and communications, and better sensors and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines. The 6H-SiC polytype is a promising wide-bandgap (Eg = 3.0 eV) semiconductor for photovoltaic applications in harsh solar environments that involve high-temperature and high-radiation conditions. The advantages of this material for this application lie in its extremely large breakdown field strength, high thermal conductivity, good electron saturation drift velocity, and stable electrical performance at temperatures as high as 600 C. This behavior makes it an attractive photovoltaic solar cell material for devices that can operate within three solar radii of the Sun.
Bailey, Sheila G.; Raffaelle, Ryne P.
Recent Advances in Solar Cell Technology
NASA Technical Reports Server (NTRS)
The advances in solar cell efficiency, radiation tolerance, and cost over the last decade are reviewed. Potential performance of thin-film solar cells in space are discussed, and the cost and the historical trends in production capability of the photovoltaics industry are considered with respect to the requirements of space power systems. Concentrator cells with conversion efficiency over 30%, and nonconcentrating solar cells with efficiency over 25% are now available, and advanced radiation-tolerant cells and lightweight, thin-film arrays are both being developed. Nonsolar applications of solar cells, including thermophotovoltaics, alpha- and betavoltaics, and laser power receivers, are also discussed.
Landis, Geoffrey A.; Bailey, Sheila G.; Piszczor, Michael F., Jr.
Silicon solar cell fabrication technology
NASA Technical Reports Server (NTRS)
The laser cell scanner was used to characterize a number of solar cells made in various materials. An electron beam-induced current (EBIC) study was performed using a stereoscan scanning electron microscope. Planar p-n junctions were analyzed. A theory for the EBIC based on the analytical solution of the ambipolar diffusion equation under the influence of electron beam excitation parameter z (which is related to beam penetration), the junction depth Z sub j, the beam current and the surface recombination, was formulated and tested. The effect of a grain boundary was studied.
Stafsudd, O. M.
Chlorine and bromine solar neutrino experiments
The solar neutrino experiment based upon the neutrino capture reaction /sup 37/Cl (..nu.., e/sup -/) /sup 37/Ar has been in operation in the Homestake Gold Mine at Lead, South Dakota since 1967. The results of this experiment are well known, and have been reported most recently to the solar neutrino conference at Lead in 1984. We report here the latest results from this experiment. A radiochemical neutrino detector based upon the neutrino capture reaction /sup 81/Br (..nu.., e/sup -/) /sup 81/Kr* ..-->.. /sup 81/Kr has recently been shown to be feasible. Our plans for performing a full scale test of the method using the Homestake chlorine detector are discussed briefly. 8 refs.
Davis, R. Jr.; Cleveland, B.T.; Rowley, J.K.
TROPIX: A solar electric propulsion flight experiment
NASA Technical Reports Server (NTRS)
The Transfer Orbit Plasma Interaction Experiment (TROPIX) is a proposed scientific experiment and flight demonstration of a solar electric propulsion vehicle. Its mission goals are to significantly increase our knowledge of Earth's magnetosphere and its associated plasma environment and to demonstrate an operational solar electric upper stage (SEUS) for small launch vehicles. The scientific investigations and flight demonstration technology experiments are uniquely interrelated because of the spacecraft's interaction with the surrounding environment. The data obtained will complement previous studies of the Earth's magnetosphere and space plasma environment by supplying the knowledge necessary to attain the strategic objectives of the NASA Office of Space Science. This first operational use of a primary ion propulsion vehicle, designed to withstand the harsh environments from low Earth orbit to geosynchronous Earth orbit, may lead to the development of a new class of electric propulsion upper stages or space-based transfer vehicles and may improve future spacecraft design and safety.
Hickman, J. Mark; Hillard, G. Barry; Oleson, Steven R.
heat treatment for solar cells
NASA Astrophysics Data System (ADS)
CdTe is an important compound semiconductor for solar cells, and its use in nanowire-based heterostructures may become a critical requirement, owing to the potential scarcity of tellurium. The effects of the CdCl2 heat treatment are investigated on the physical properties of vertically aligned ZnO/CdTe core-shell nanowire arrays grown by combining chemical bath deposition with close space sublimation. It is found that recrystallization phenomena are induced by the CdCl2 heat treatment in the CdTe shell composed of nanograins: its crystallinity is improved while grain growth and texture randomization occur. The presence of a tellurium crystalline phase that may decorate grain boundaries is also revealed. The CdCl2 heat treatment further favors the chlorine doping of the CdTe shell with the formation of chlorine A-centers and can result in the passivation of grain boundaries. The absorption properties of ZnO/CdTe core-shell nanowire arrays are highly efficient, and more than 80% of the incident light can be absorbed in the spectral range of the solar irradiance. The resulting photovoltaic properties of solar cells made from ZnO/CdTe core-shell nanowire arrays covered with CuSCN/Au back-side contact are also improved after the CdCl2 heat treatment. However, recombination and trap phenomena are expected to operate, and the collection of the holes that are mainly photo-generated in the CdTe shell from the CuSCN/Au back-side contact is presumably identified as the main critical point in these solar cells.
Consonni, Vincent; Renet, S�bastien; Garnier, J�r�me; Gergaud, Patrice; Art�s, Lluis; Michallon, J�r�me; Rapenne, Laetitia; Appert, Estelle; Kaminski-Cachopo, Anne
Status of multijunction solar cells
NASA Technical Reports Server (NTRS)
This paper describes Applied Solar's present activity on Multijunction (MJ) space cells. We have worked on a variety of MJ cells, both monolithic and mechanically stacked. In recent years, most effort has been directed to GaInP2/GaAs monolithic cells, grown on Ge substrates, and the status of this cell design will be reviewed here. MJ cells are in demand to provide satellite power because of the acceptance of the overwhelming importance of high efficiency to reduce the area, weight and cost of space PV power systems. The need for high efficiencies has already accelerated the production of GaAs/Ge cells, with efficiencies 18.5-19%. When users realized that MJ cells could provide higher efficiencies (from 22% to 26%) with only fractional increase in costs, the demand for production MJ cells increased rapidly. The main purpose of the work described is to transfer the MOCVD growth technology of MJ high efficiency cells to a production environment, providing all the space requirements of users.
Yeh, Y. C. M.; Chu, C. L.
Laser scanning of experimental solar cells
An instrument is described which measures and displays the response of the solar cell to a precisely positioned spot of HeNe laser light. By scanning the spot across the cell surface, one can create a map of the spatial variation in response of the cell. This map allows one to isolate flaws in cell contact integrity, locate open top surface grid lines, and evaluate fundamental junction performance. The system is useful for identifying and locating changes in the cell as it progresses through various experiments (e.g. stability studies). The laser scanner system is designed to be flexible and can accommodate different types of solar cell materials and a wide range of spot and scan sizes. Several modes of operation of the equipment are described, and results from two photovoltaic materials (CdS/Cu/sub 2/S and Zn/sub 3/P/sub 2/) are presented which demonstrate the capabilities of the system. Finally some of the proposed future uses of the system are discussed. 6 refs.
Plunkett, B.C.; Lasswell, P.G.
NASA Astrophysics Data System (ADS)
The formation of stable, low resistance and nonrectifying contacts to Cu2ZnSnS4 (CZTS) thin film photovoltaic material are the major and critical challenges associated with its effect over the output performance of fabricated solar cells. The solution of continuity equation in one dimension for a soda lime glass substrates (SLG) |Mo | CZTS | CdS | ZnO:Al cell structure is considered in the simulation of its current-voltage characteristics that is governed by the back contact material, acceptor concentration as well as thickness of the CZTS layer. Our primary simulation shows a 6.44% efficiency of the CZTS solar cell which is comparable to reported experimental data if these parameters are not optimized. However, by optimizing them a simulated conversion efficiency as high as 13.41% (Voc=1.002 V, Jsc=19.31 mA/cm2, fill factor (FF)=69.35%) could be achievable. The solar cell with a back contact metal work function of 5.5 eV, an absorber layer's thickness of 2.68 ?m and an acceptor concentration of 5�1016 cm-3 were optimum. The presented optimization is ideal and subject to experimental verification with a precise control of the process parameters along with reduced surface as well as bulk recombination, secondary phases and thermalization losses.
Patel, Malkeshkumar; Ray, Abhijit
Supramolecular photochemistry and solar cells
Supramolecular photochemistry as well as solar cells are fascinating topics of current interest in Inorganic Photochemistry and very active research fields which have attracted wide attention in last two decades. A brief outline of the investigations in these fields carried out in our Laboratory of Inorganic Photochemistry and Energy Conversion is given here with no attempt of an exhaustive coverage of the literature. The emphasis is placed on recent work and information on the above mentioned subjects. Three types of supramolecular systems have been the focus of this work: (i) cage-type coordination compounds; (ii) second-sphere coordination compounds, exemplified by ion-pair photochemistry of cobalt complexes and (iii) covalently-linked systems. In the latter, modulation of the photoluminescence and photochemistry of some rhenium complexes are discussed. Solar energy conversion and development of thin-layer photoelectrochemical solar cells based on sensitization of nanocrystalline semiconductor films by some ruthenium polypyridyl complexes are presented as an important application that resulted from specifically engineered artificial assemblies. PMID:10932106
Silicon Solar Cell Process Development, Fabrication and Analysis
NASA Technical Reports Server (NTRS)
Ribbon to Ribbon (RTR) solar cells processed from polycrystalline feedstock showed maximum AMO efficiency of 5.6%. Solar cells from single crystalline feedstock showed slightly higher efficiency than those from polycrystalline feedstock, indicating maximum efficiency of about 6.6% with SiO AR coating. Single crystalline control cells gave 11-12% AMO efficiencies demonstrating that the poor performance of the RTR solar was due to the low quality of material itself. Dendritic web solar cells from the standard process showed maximum AMO efficiency of 9.8% while efficiency of control solar cells were around 11-12%. Web solar cells from back surface field (BSF) process indicated maximum AMO efficiency of 10.9%. Some improvement in open circuit voltage was noticed from the BSF process. Small light spot scanning experiments were carried out on the solar cells from Wacker Silso, EFG, RTR, and dendritic web ribbons. Photoresponse results provided information on localized cell performance and grain size in polycrystalline material, and agreed quite well with the cell performance data, such as efficiency, minority carrier diffusion length, and spectral response.
Yoo, H. I.; Iles, P. A.; Tanner, D. P.
Energy Conversion: Nano Solar Cell
NASA Astrophysics Data System (ADS)
Problems of fossil-fuel-induced climate change have sparked a demand for sustainable energy supply for all sectors of economy. Most laboratories continue to search for new materials and new technique to generate clean energy at affordable cost. Nanotechnology can play a major role in solving the energy problem. The prospect for solar energy using Si-based technology is not encouraging. Si photovoltaics can produce electricity at 20-30 c//kWhr with about 25% efficiency. Nanoparticles have a strong capacity to absorb light and generate more electrons for current as discovered in the recent work of organic and dye-sensitized cell. Using cheap preparation technique such as screen-printing and self-assembly growth, organic cells shows a strong potential for commercialization. Thin Films research group at National University Malaysia has been actively involved in these areas, and in this seminar, we will present a review works on nanomaterials for solar cells and particularly on hybrid organic solar cell based on ZnO nanorod arrays. The organic layer consisting of poly[2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEHPPV) and [6, 6]-phenyl C61-butyric acid 3-ethylthiophene ester (PCBE) was spin-coated on ZnO nanorod arrays. ZnO nanorod arrays were grown on FTO glass substrates which were pre-coated with ZnO nanoparticles using a low temperature chemical solution method. A gold electrode was used as the top contact. The device gave a short circuit current density of 2.49�10-4 mA/cm2 and an open circuit voltage of 0.45 V under illumination of a projector halogen light at 100 mW/cm2.
Yahaya, Muhammad; Yap, Chi Chin; Mat Salleh, Muhamad
Thermal stress cycling of GaAs solar cells
A thermal cycling experiment was performed on GaAs solar cells to establish the electrical and structural integrity of these cells under the temperature conditions of a simulated low-Earth orbit of 3-year duration. Thirty single junction GaAs cells were obtained and tests were performed to establish the beginning-of-life characteristics of these cells. The tests consisted of cell I-V power output curves,
B. K. Janousek; R. W. Francis; J. P. Wendt
Immersion Cooling of Photovoltaic Cells in Highly Concentrated Solar Beams.
??Concentrated solar radiation can be utilized to generate electrical power from photovoltaic cells, but concentrated solar radiation increases the photovoltaic cell�s temperature. This increase in� (more)
Darwish, Ahmed
Solar cell system having alternating current output
NASA Technical Reports Server (NTRS)
A monolithic multijunction solar cell was modified by fabricating an integrated circuit inverter on the back of the cell to produce a device capable of generating an alternating current output. In another embodiment, integrated curcuit power conditioning electronics was incorporated in a module containing a solar cell power supply.
Evans, J. C., Jr. (inventor)
Solar Cell Modules With Improved Backskin
A laminated solar cell module comprises a front light transmitting support, a plurality of interconnected solar cells encapsulated by a light-transmitting encapsulant material, and an improved backskin formed of an ionomer/nylon alloy. The improved backskin has a toughness and melting point temperature sufficiently great to avoid any likelihood of it being pierced by any of the components that interconnect the solar cells.
Gonsiorawski, Ronald C. (Danvers, MA)
Bypass diodes for solar cells are described. In one embodiment, a bypass diode for a solar cell includes a substrate of the solar cell. A first conductive region is disposed above the substrate, the first conductive region of a first conductivity type. A second conductive region is disposed on the first conductive region, the second conductive region of a second conductivity type opposite the first conductivity type.
Rim, Seung Bum (Palo Alto, CA); Kim, Taeseok (San Jose, CA); Smith, David D. (Campbell, CA); Cousins, Peter J. (Menlo Park, CA)
Solar cells using quantum funnels.
Colloidal quantum dots offer broad tuning of semiconductor bandstructure via the quantum size effect. Devices involving a sequence of layers comprised of quantum dots selected to have different diameters, and therefore bandgaps, offer the possibility of funneling energy toward an acceptor. Here we report a quantum funnel that efficiently conveys photoelectrons from their point of generation toward an intended electron acceptor. Using this concept we build a solar cell that benefits from enhanced fill factor as a result of this quantum funnel. This concept addresses limitations on transport in soft condensed matter systems and leverages their advantages in large-area optoelectronic devices and systems. PMID:21827197
Kramer, Illan J; Levina, Larissa; Debnath, Ratan; Zhitomirsky, David; Sargent, Edward H
Thin GaAs solar cell structures
This patent describes a solar cell, comprising: a layer of p-type gallium arsenide having a thickness of not greater than about 0.5 micrometers; a layer of n-type gallium arsenide. The layer of p-type gallium arsenide and the layer of n-type gallium arsenide together constitutes an active semiconductor solar cell; a glass cover in contact with the active semiconductor solar cell. The solar cell has no charge recombination inhibitory layer in contact with the layer of p-type gallium arsenide.
Ellion, M.E.; Wolff, G.
Fabrication and Characterization of Organic Solar Cells.
??Bulk heterojunction organic solar cells have recently drawn tremendous attention because of their technological advantages for actualization of large-area and cost effective fabrication. Two important� (more)
Yengel, Emre
Good edge extraction from temporal series of solar images is fundamental in the solar astrolabe experiment. Noise and spots in images cause however, difficulties to extract an accurate solar edge. We present in this paper a new image-processing method which solves this problem and thus improves the characteristics of the solar astrolabe experiment. The method is based upon the use
A. Irbah; M. Bouzaria; L. Lakhal; R. Moussaoui; J. Borgnino; F. Laclare; C. Delmas
Front contact solar cell with formed emitter
A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.
Cousins, Peter John (Menlo Park, CA)
GPS patch antenna with photovoltaic solar cells for vehicular applications
This paper describes the application of photovoltaic (PV) solar cells in planar antenna structures. The radiating patch element of a planar antenna is replaced by a solar cell. The original feature of a solar cell (DC current generation) remains, but additionally the cell is now able to receive and transmit electromagnetic waves. Both single solar cells as well as solar
Norbert Henze; Andre Giere; Henning Fr�chting; Pascal Hofmann
Current status of silicon solar cell technology
NASA Technical Reports Server (NTRS)
In quest of higher efficiency, major progress has occurred in solar cell technology. Cell efficiency has climbed about 50 percent. Technical approaches leading to increased output include back surface fields, shallow junctions, improved antireflection coatings, surface texturizing, and fine grid patterns on the cell surface. The status of current solar cell technology and its incorporation into cell production is discussed. Research and development leading to improved performance and reduced cost are also described.
Brandhorst, H. W., Jr.
Current and lattice matched tandem solar cell
A multijunction (cascade) tandem photovoltaic solar cell device is fabricated of a Ga.sub.x In.sub.1-x P (0.505.ltoreq.X.ltoreq.0.515) top cell semiconductor lattice matched to a GaAs bottom cell semiconductor at a low-resistance heterojunction, preferably a p+/n+ heterojunction between the cells. The top and bottom cells are both lattice matched and current matched for high efficiency solar radiation conversion to electrical energy.
Olson, Jerry M. (Lakewood, CO)
New materials for solar cells - Tandem cells
NASA Astrophysics Data System (ADS)
Cost efficiency in the manufacturing processes of the solar cell panels is discussed, noting the utilization of the III-V compound semiconductors (such as InSb or Ge) instead of silicon or gallium arsenide which have a complicated and expensive technology. A computation program is presented for a p-n junction using a set of nonlinear differential equations and taking into consideration such parameters as the mobility, the life space and the forbidden band. It is concluded that new, economic technologies should be directed toward blocking the UV light, acrylic elastomers, waterproof wood and paper materials and cost efficient silicon and fluorocarbon materials.
Dolocan, V.
Method for processing silicon solar cells
The instant invention teaches a novel method for fabricating silicon solar cells utilizing concentrated solar radiation. The solar radiation is concentrated by use of a solar furnace which is used to form a front surface junction and back-surface field in one processing step. The present invention also provides a method of making multicrystallline silicon from amorphous silicon. The invention also teaches a method of texturing the surface of a wafer by forming a porous silicon layer on the surface of a silicon substrate and a method of gettering impurities. Also contemplated by the invention are methods of surface passivation, forming novel solar cell structures, and hydrogen passivation.
Tsuo, Y. Simon (Golden, CO); Landry, Marc D. (Lafayette, CO); Pitts, John R. (Lakewood, CO)
Method for processing silicon solar cells
The instant invention teaches a novel method for fabricating silicon solar cells utilizing concentrated solar radiation. The solar radiation is concentrated by use of a solar furnace which is used to form a front surface junction and back-surface field in one processing step. The present invention also provides a method of making multicrystalline silicon from amorphous silicon. The invention also teaches a method of texturing the surface of a wafer by forming a porous silicon layer on the surface of a silicon substrate and a method of gettering impurities. Also contemplated by the invention are methods of surface passivation, forming novel solar cell structures, and hydrogen passivation. 2 figs.
Tsuo, Y.S.; Landry, M.D.; Pitts, J.R.
Operational experience from solar thermal energy projects
NASA Astrophysics Data System (ADS)
Over the past few years, Sandia National Laboratories were involved in the design, construction, and operation of a number of DOE-sponsored solar thermal energy systems. Among the systems currently in operation are several industrial process heat projects and the Modular Industrial Solar Retrofit qualification test systems, all of which use parabolic troughs, and the Shenandoah Total Energy Project, which uses parabolic dishes. Operational experience has provided insight to both desirable and undesirable features of the designs of these systems. Features of these systems which are also relevant to the design of parabolic concentrator thermal electric systems are discussed. Other design features discussed are system control functions which were found to be especially convenient or effective, such as local concentrator controls, rainwash controls, and system response to changing isolation. Drive systems are also discussed with particular emphasis of the need for reliability and the usefulness of a manual drive capability.
Cameron, C. P.
Molecular weight dependent bimolecular recombination in organic solar cells
NASA Astrophysics Data System (ADS)
Charge carrier recombination is studied in operational organic solar cells made from the polymer:fullerene system PCDTBT:PC71BM (poly[N-9''-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]: [6,6]-phenyl-C70-butyric acid methyl ester). A newly developed technique High Intensity Resistance dependent PhotoVoltage is presented for reliably quantifying the bimolecular recombination coefficient independently of variations in experimental conditions, thereby resolving key limitations of previous experimental approaches. Experiments are performed on solar cells of varying thicknesses and varying polymeric molecular weights. It is shown that solar cells made from low molecular weight PCDTBT exhibit Langevin recombination, whereas suppressed (non-Langevin) recombination is found in solar cells made with high molecular weight PCDTBT.
Philippa, Bronson; Stolterfoht, Martin; White, Ronald D.; Velusamy, Marrapan; Burn, Paul L.; Meredith, Paul; Pivrikas, Almantas
Molecular weight dependent bimolecular recombination in organic solar cells.
Charge carrier recombination is studied in operational organic solar cells made from the polymer:fullerene system PCDTBT:PC71BM (poly[N-9''-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]: [6,6]-phenyl-C70-butyric acid methyl ester). A newly developed technique High Intensity Resistance dependent PhotoVoltage is presented for reliably quantifying the bimolecular recombination coefficient independently of variations in experimental conditions, thereby resolving key limitations of previous experimental approaches. Experiments are performed on solar cells of varying thicknesses and varying polymeric molecular weights. It is shown that solar cells made from low molecular weight PCDTBT exhibit Langevin recombination, whereas suppressed (non-Langevin) recombination is found in solar cells made with high molecular weight PCDTBT. PMID:25106609
Philippa, Bronson; Stolterfoht, Martin; White, Ronald D; Velusamy, Marrapan; Burn, Paul L; Meredith, Paul; Pivrikas, Almantas
New Solar Cell Power Supply System Using a Boost Type Bidirectinal DC-DC Converter
A new solar cell power supply system is presented, in which the boost type bidirectional dc-dc converter and the simple control circuit with a small monitor solar cell are employed to track the maximum power point of the solar array. It is confirmed by the experiment that the new system has sufficiently precise tracking operation performance and satisfactorily high power
Hirofumi Matsuo; Fujio Kurokawa
Monolithic cells for solar fuels.
Hybrid energy generation models based on a variety of alternative energy supply technologies are considered the best way to cope with the depletion of fossil energy resources and to limit global warming. One of the currently missing technologies is the mimic of natural photosynthesis to convert carbon dioxide and water into chemical fuel using sunlight. This idea has been around for decades, but artificial photosynthesis of organic molecules is still far away from providing real-world solutions. The scientific challenge is to perform in an efficient way the multi-electron transfer reactions of water oxidation and carbon dioxide reduction using holes and single electrons generated in an illuminated semiconductor. In this tutorial review the design of photoelectrochemical (PEC) cells that combine solar water oxidation and CO2 reduction is discussed. In such PEC cells simultaneous transport and efficient use of light, electrons, protons and molecules has to be managed. It is explained how efficiency can be gained by compartmentalisation of the water oxidation and CO2 reduction processes by proton exchange membranes, and monolithic concepts of artificial leaves and solar membranes are presented. Besides transferring protons from the anode to the cathode compartment the membrane serves as a molecular barrier material to prevent cross-over of oxygen and fuel molecules. Innovative nano-organized multimaterials will be needed to realise practical artificial photosynthesis devices. This review provides an overview of synthesis techniques which could be used to realise monolithic multifunctional membrane-electrode assemblies, such as Layer-by-Layer (LbL) deposition, Atomic Layer Deposition (ALD), and porous silicon (porSi) engineering. Advances in modelling approaches, electrochemical techniques and in situ spectroscopies to characterise overall PEC cell performance are discussed. PMID:24526085
Rong�, Jan; Bosserez, Tom; Martel, David; Nervi, Carlo; Boarino, Luca; Taulelle, Francis; Decher, Gero; Bordiga, Silvia; Martens, Johan A
Introduction to basic solar cell measurements
NASA Technical Reports Server (NTRS)
The basic approaches to solar cell performance and diagnostic measurements are described. The light sources, equipment for I-V curve measurement, and the test conditions and procedures for performance measurement are detailed. Solar cell diagnostic tools discussed include analysis of I-V curves, series resistance and reverse saturation current determination, spectral response/quantum yield measurement, and diffusion length/lifetime determination.
Brandhorst, H. W., Jr.
Thin solar cell and lightweight array
NASA Technical Reports Server (NTRS)
A thin, lightweight solar cell that utilizes front contact metallization is presented. Both the front light receiving surface of the solar cell and the facing surface of the cover glass are recessed to accommodate this metallization. This enables the two surfaces to meet flush for an optimum seal.
Brandhorst, Henry W., Jr. (inventor); Weinberg, Irving (inventor)
EE580 Solar Cells Todd J. Kaiser
that makes electrons move (difference in height makes water flow) 9Montana State University: Solar Cells · Symbolic information: electronics Montana State University: Solar Cells Lecture 7: EE Fundamentals 2 Review · Electric charge is produced by electrons and protons · Electrons are negatively charged and protons
Kaiser, Todd J.
Nanowire-based All Oxide Solar Cells
We present an all-oxide solar cell fabricated from vertically oriented zinc oxide nanowires and cuprous oxide nanoparticles. Our solar cell consists of vertically oriented n-type zinc oxide nanowires, surrounded by a film constructed from p-type cuprous oxide nanoparticles. Our solution-based synthesis of inexpensive and environmentally benign oxide materials in a solar cell would allow for the facile production of large-scale photovoltaic devices. We found that the solar cell performance is enhanced with the addition of an intermediate oxide insulating layer between the nanowires and the nanoparticles. This observation of the important dependence of the shunt resistance on the photovoltaic performance is widely applicable to any nanowire solar cell constructed with the nanowire array in direct contact with one electrode.
Yang*, Benjamin D. Yuhas and Peidong; Yang, Peidong
Planar multijunction high voltage solar cells
NASA Technical Reports Server (NTRS)
Technical considerations, preliminary results, and fabrication details are discussed for a family of high-voltage planar multi-junction (PMJ) solar cells which combine the attractive features of planar cells with conventional or interdigitated back contacts and the vertical multijunction (VMJ) solar cell. The PMJ solar cell is internally divided into many voltage-generating regions, called unit cells, which are internally connected in series. The key to obtaining reasonable performance from this device was the separation of top surface field regions over each active unit cell. Using existing solar cell fabricating methods, output voltages in excess of 20 volts per linear centimeter are possible. Analysis of the new device is complex, and numerous geometries are being studied which should provide substantial benefits in both normal sunlight usage as well as with concentrators.
Evans, J. C., Jr.; Chai, A. T.; Goradia, C.
High-Temperature Solar Cell Development
NASA Technical Reports Server (NTRS)
The vast majority of satellites and near-earth probes developed to date have relied upon photovoltaic power generation. If future missions to probe environments close to the sun will be able to use photovoltaic power, solar cells that can function at high temperatures, under high light intensity, and high radiation conditions must be developed. For example, the equilibrium temperature of a Mercury surface station will be about 450 C, and the temperature of solar arrays on the proposed "Solar Probe" mission will extend to temperatures as high as 2000 C (although it is likely that the craft will operate on stored power rather than solar energy during the closest approach to the sun). Advanced thermal design principles, such as replacing some of the solar array area with reflectors, off-pointing, and designing the cells to reflect rather than absorb light out of the band of peak response, can reduce these operating temperature somewhat. Nevertheless, it is desirable to develop approaches to high-temperature solar cell design that can operate under temperature extremes far greater than today's cells. Solar cells made from wide bandgap (WBG) compound semiconductors are an obvious choice for such an application. In order to aid in the experimental development of such solar cells, we have initiated a program studying the theoretical and experimental photovoltaic performance of wide bandgap materials. In particular, we have been investigating the use of GaP, SiC, and GaN materials for space solar cells. We will present theoretical results on the limitations on current cell technologies and the photovoltaic performance of these wide-bandgap solar cells in a variety of space conditions. We will also give an overview of some of NASA's cell developmental efforts in this area and discuss possible future mission applications.
Landis, Geoffrey A.; Raffaelle, Ryne P.; Merritt, Danielle
Solar cells for terrestrial applications
NASA Technical Reports Server (NTRS)
The power efficiency curves of photovoltaic solar cells were investigated as a function of the forbidden energy gap (E sub g) and the current-voltage characteristic of the diode. Minority carrier injection, depletion layer recombination, and interface recombination terms were considered in models for the I-V characteristic. The collection efficiency for photons with energy between (E sub g) and an upper energy cutoff (E sub w) was assumed to be 100% and zero otherwise. Results are presented in terms of a single parameter related to the ratio of depletion layer width and minority carrier diffusion length. It was found that increasing depletion layer recombination shifts the efficiency curves to larger values of the energy without changing the shape of the efficiency curve appreciably. It is believed that similar results would be obtained whenever the quality factors in the exponential energy gap and forward bias terms are equal.
Chernow, F.
Porphyrin-sensitized solar cells.
Nature has chosen chlorophylls in plants as antennae to harvest light for the conversion of solar energy in complicated photosynthetic processes. Inspired by natural photosynthesis, scientists utilized artificial chlorophylls - the porphyrins - as efficient centres to harvest light for solar cells sensitized with a porphyrin (PSSC). After the first example appeared in 1993 of a porphyrin of type copper chlorophyll as a photosensitizer for PSSC that achieved a power conversion efficiency of 2.6%, no significant advance of PSSC was reported until 2005; beta-linked zinc porphyrins were then reported to show promising device performances with a benchmark efficiency of 7.1% reported in 2007. Meso-linked zinc porphyrin sensitizers in the first series with a push-pull framework appeared in 2009; the best cell performed comparably to that of a N3-based device, and a benchmark 11% was reported for a porphyrin sensitizer of this type in 2010. With a structural design involving long alkoxyl chains to envelop the porphyrin core to suppress the dye aggregation for a push-pull zinc porphyrin, the PSSC achieved a record 12.3% in 2011 with co-sensitization of an organic dye and a cobalt-based electrolyte. The best PSSC system exhibited a panchromatic feature for light harvesting covering the visible spectral region to 700 nm, giving opportunities to many other porphyrins, such as fused and dimeric porphyrins, with near-infrared absorption spectral features, together with the approach of molecular co-sensitization, to enhance the device performance of PSSC. According to this historical trend for the development of prospective porphyrin sensitizers used in PSSC, we review systematically the progress of porphyrins of varied kinds, and their derivatives, applied in PSSC with a focus on reports during 2007-2012 from the point of view of molecular design correlated with photovoltaic performance. PMID:23023240
Li, Lu-Lin; Diau, Eric Wei-Guang
Silicon solar cell efficiency: Practice and promise
NASA Technical Reports Server (NTRS)
The maximum efficiency of silicon solar cells was calculated and yielded a value near 18%. Additionally, the performance of these high efficiency cells in a synchronous orbit radiation field was calculated and it is suggested that these cells would be superior to present silicon cells. The performance of conventional cells was analyzed and several areas in which performance gains may be achieved are discussed. These areas include improvements in diffused region profile, in reduction of excess forward currents in cells made from low resistivity material, and in the theory for describing complex solar cell structures.
Brandhorst, H. W., Jr.
Orbiting solar observatory 8 high resolution ultraviolet spectrometer experiment
NASA Technical Reports Server (NTRS)
Oscillations, physical properties of the solar atmosphere, motions in the quiet solar atmosphere, coronal holes, motions in solar active regions, solar flares, the structure of plage regions, an atlas, and aeronomy are summarized. Photometric sensitivity, scattered light, ghosts, focus and spectral resolution, wavelength drive, photometric sensitivity, and scattered light, are also summarized. Experiments are described according to spacecraft made and experiment type. Some of the most useful data reduction programs are described.
Radiochemical Solar Neutrino Experiments - Successful and Otherwise.
Over the years, several different radiochemical systems have been proposed as solar neutrino detectors. Of these, two achieved operating status and obtained important results that helped to define the current field of neutrino physics: the first solar-neutrino experiment, the Chlorine Detector ({sup 37}Cl) that was developed by chemist Raymond Davis and colleagues at the Homestake Mine, and the subsequent Gallium ({sup 71}Ga) Detectors that were operated by (a) the SAGE collaboration at the Baksan Laboratory and (b) the GALLEX/GNO collaborations at the Gran Sasso National Laboratory. These experiments have been extensively discussed in the literature and in many previous International Neutrino Conferences. In this paper, I present important updates to the results from SAGE and GALLEX/GNO. I also review the principles of the radiochemical detectors and briefly describe several different detectors that have been proposed. In light of the well-known successes that have been subsequently obtained by real-time neutrino detectors such as Kamiokande, Super-Kamiokande, SNO, and KamLAND, I do not anticipate that any new radiochemical neutrino detectors will be built. At present, only SAGE is still operating; the Chlorine and GNO radiochemical detectors have been decommissioned and dismantled.
Nanocomposite enables sensitized solar cell
NASA Astrophysics Data System (ADS)
Dye Sensitized solar cells (DSSCs) are a promising candidate for next generation photovoltaic panels due to their low cost, easy fabrication process, and relative high efficiency. Despite considerable effort on the advancement of DSSCs, the efficiency has been stalled for nearly a decade due to the complex interplay among various DSSC components. DSSCs consist of a photoanode on a conducting substrate, infiltrated dye for light absorption and electron injection, and an electrolyte to regenerate the dye. On the photoanode is a high band-gap semiconducting material, primarily of a nanostructure morphology of titanium (II) dioxide (TiO2), dye molecules whose molar absorption is typically in the visible spectrum, are adsorbed onto the surface of TiO 2. To improve the current DSSCs, there are many parameters that can be investigated. In a conventional DSSC, a thick semiconducting layer such as the nanoparticle TiO2 layer induces charge separation efficiently while concurrently increasing the charge transport distance, leading the cell to suffer from more charge recombination and deterioration in charge collection efficiency. To improve on this limitation, TiO2 nanowires (NW) and nanotubes (NT) are explored to replace the nanoparticle photoanode. One-dimensional nanostructures are known for the excellent electron transport properties as well as maintaining a relatively high surface area. Hence one of the focuses of this thesis explores at using different morphologies and composition of TiO2 nanostructures to enhance electron collection efficiency. Another challenge in conventional DSSCs is the limit in light absorption of solar irradiation. Dyes are limited to absorption only in the visible range, and have a low molar absorption coefficient in the near infrared (NIR). Tuning dyes is extremely complicated and may have more disadvantages than simply by extending light harvesting. Therefore our strategy is to incorporate quantum dots to replace the dye, as well as prepare a cell for the possibility of co-sensitization, thereby extending the absorption of light in the visible and NIR. The first phase of the thesis involves the synthesis and characterization of the materials used for the cell. We successfully synthesized TiO2 nanowires and nanotubes and characterized them for the use as the photoanode. Both one-dimensional structures proved to have low resistivity, chemical stability, and high density. We also synthesized lead (II) sulfide (PbS) quantum dots (QDs) and explored at modifying their diameter in order to properly control their light harvesting potential into the NIR region. The electron transport kinetics proved to be faster in one-dimensional nanostructure due to their high crystallinity order and reduced elastic scattering of the electrons during transport. Furthermore, quantum dots were synthesized such that their band-gap allowed for the absorption of NIR light. This result extended the harvesting potential of our solar cell and suggests the possibility for co-sensitization in DSSCs using dye molecules and quantum dots. Hence, the focus of this thesis work is to systematically explore a transformative way to fundamentally enhance charge transport and extend light absorption by in the incorporation of two sensitizing agents.
Phuyal, Dibya D.
Tandem photovoltaic solar cells and increased solar energy conversion efficiency
NASA Technical Reports Server (NTRS)
Tandem photovoltaic cells, as proposed by Jackson (1955) to increase the efficiency of solar energy conversion, involve the construction of a system of stacked p/n homojunction photovoltaic cells composed of different semiconductors. It had been pointed out by critics, however, that the total power which could be extracted from the cells in the stack placed side by side was substantially greater than the power obtained from the stacked cells. A reexamination of the tandem cell concept in view of the development of the past few years is conducted. It is concluded that the use of tandem cell systems in flat plate collectors, as originally envisioned by Jackson, may yet become feasible as a result of the development of economically acceptable solar cells for large scale terrestrial power generation.
Loferski, J. J.
Semiconductor quantum dot-sensitized solar cells
Semiconductor quantum dots (QDs) have been drawing great attention recently as a material for solar energy conversion due to their versatile optical and electrical properties. The QD-sensitized solar cell (QDSC) is one of the burgeoning semiconductor QD solar cells that shows promising developments for the next generation of solar cells. This article focuses on recent developments in QDSCs, including 1) the effect of quantum confinement on QDSCs, 2) the multiple exciton generation (MEG) of QDs, 3) fabrication methods of QDs, and 4) nanocrystalline photoelectrodes for solar cells. We also make suggestions for future research on QDSCs. Although the efficiency of QDSCs is still low, we think there will be major breakthroughs in developing QDSCs in the future. PMID:24191178
Tian, Jianjun; Cao, Guozhong
Silicon solar cells improved by lithium doping
NASA Technical Reports Server (NTRS)
Results of conference on characteristics of lithium-doped silicon solar cells and techniques required for fabrication indicate that output of cells has been improved to point where cells exhibit radiation resistance superior to those currently in use, and greater control and reproducibility of cell processing have been achieved.
Berman, P. A.
Development and fabrication of a solar cell junction processing system
NASA Technical Reports Server (NTRS)
A solar cell junction processing system was developed and fabricated. A pulsed electron beam for the four inch wafers is being assembled and tested, wafers were successfully pulsed, and solar cells fabricated. Assembly of the transport locks is completed. The transport was operated successfully but not with sufficient reproducibility. An experiment test facility to examine potential scaleup problems associated with the proposed ion implanter design was constructed and operated. Cells were implanted and found to have efficiency identical to the normal Spire implant process.
Bunker, S.
Comprehensive silicon solar-cell computer modeling
NASA Technical Reports Server (NTRS)
A comprehensive silicon solar cell computer modeling scheme was developed to perform the following tasks: (1) model and analysis of the net charge distribution in quasineutral regions; (2) experimentally determined temperature behavior of Spire Corp. n+pp+ solar cells where n+-emitter is formed by ion implantation of 75As or 31P; and (3) initial validation results of computer simulation program using Spire Corp. n+pp+ cells.
Lamorte, M. F.
Emitter wrap-through solar cell
The authors present a new solar cell concept (emitter wrap-through or EWT) for a back-contact cell. The cell has laser-drilled vias to wrap the emitter on the front surface to contacts on the back surface and uses a potentially low-cost process sequence. Modeling calculations show that efficiencies of 18 and 21% are possible with large-area solar-grade multi- and monocrystalline silicon
James M. Gee; W. Kent Schubert; Paul A. Basore
Development of gallium arsenide solar cells
NASA Technical Reports Server (NTRS)
The potential of ion implantation as a means of developing gallium arsenide solar cells with high efficiency performance was investigated. Computer calculations on gallium arsenide cell characteristics are presented to show the effects of surface recombination, junction space-charge recombination, and built-in fields produced by nonuniform doping of the surface region. The fabrication technology is summarized. Electrical and optical measurements on samples of solar cells are included.
Dye-sensitized Solar Cells for Solar Energy Harvesting
NASA Astrophysics Data System (ADS)
Dye-sensitized solar cells (DSSCs) also known as Gratzel cells, have attracted the interests of researchers to a great extent because of its cost effective and easy manufacturing process without involving highly sophisticated lithographic technique and high cost raw materials as usually seen in conventional solar cell. Based on simple photo-electrochemical process, it has got immense potential in converting solar energy to electrical power in remote and desert area where the supply of conventional power is not possible. The overall peak power-production efficiency of dye-sensitized solar cells has been reported around 11 percent, so they are best suited to low-density applications and the price-to-performance ratio obtained through these solar cells is superior to others. DSSCs have ability to absorb even diffused sunlight and therefore work in cloudy whether as well without much impact over the efficiency. The present communication deals with a review of our work on DSSCs wherein we have used cost effective natural dyes/pigments as a sensitizer of nc-TiO2 and discussed about various key factors affecting the conversion efficiency of DSSC.
Roy, M. S.; Deol, Y. S.; Kumar, Manish; Prasad, Narottam; Janu, Yojana
Development of GaAs solar cells
NASA Technical Reports Server (NTRS)
Calculations of GaAs solar cell output parameters were refined and a computer model was developed for parameter optimization. The results were analyzed to determine the material characteristics required for a high efficiency solar cell. Calculated efficiencies for a P/N cell polarity are higher than an N/P cell. Both cell polarities show efficiency to have a larger dependence on short circuit current than an open circuit voltage under nearly all conditions considered. The tolerances and requirements of a cell fabrication process are more critical for an N/P type than for a P/N type cell. Several solar cell fabrication considerations relative to junction formation using ion implantation are also discussed.
Mcnally, P. J.
Cascade solar cell having conductive interconnects
Direct ohmic contact between the cells in an epitaxially grown cascade solar cell is obtained by means of conductive interconnects formed through grooves etched intermittently in the upper cell. The base of the upper cell is directly connected by the conductive interconnects to the emitter of the bottom cell. The conductive interconnects preferably terminate on a ledge formed in the base of the upper cell.
Borden, Peter G. (Menlo Park, CA); Saxena, Ram R. (Saratoga, CA)
Teachers' Domain: Inside a Solar Cell
NSDL National Science Digital Library
This interactive Flash tutorial shows how photovoltaic cells in solar panels convert sunlight into electrical current. It provides a close-up look at each layer of the basic solar panel, with particular emphasis on how electrons cross over the junction that joins the two silicon layers in the cell. When the concentration of negative and positive charge between the two layers reaches equilibrium, an electric field is produced -- the solar cell is ready to capture photons. Teachers' Domain is a collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.
Heterojunction solar cell with passivated emitter surface
A high-efficiency heterojunction solar cell wherein a thin emitter layer (preferably Ga.sub.0.52 In.sub.0.48 P) forms a heterojunction with a GaAs absorber layer. A passivating window layer of defined composition is disposed over the emitter layer. The conversion efficiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the window layer.
Olson, Jerry M. (Lakewood, CO); Kurtz, Sarah R. (Golden, CO)
Methods of fabricating bypass diodes for solar cells are described. In once embodiment, a method includes forming a first conductive region of a first conductivity type above a substrate of a solar cell. A second conductive region of a second conductivity type is formed on the first conductive region. In another embodiment, a method includes forming a first conductive region of a first conductivity type above a substrate of a solar cell. A second conductive region of a second conductivity type is formed within, and surrounded by, an uppermost portion of the first conductive region but is not formed in a lowermost portion of the first conductive region.
Rim, Seung Bum; Kim, Taeseok; Smith, David D; Cousins, Peter J
Heterojunction solar cell with passivated emitter surface
A high-efficiency heterojunction solar cell is described wherein a thin emitter layer (preferably Ga[sub 0.52]In[sub 0.48]P) forms a heterojunction with a GaAs absorber layer. A passivating window layer of defined composition is disposed over the emitter layer. The conversion efficiency of the solar cell is at least 25.7%. The solar cell preferably includes a passivating layer between the substrate and the absorber layer. An anti-reflection coating is preferably disposed over the window layer. 1 fig.
Olson, J.M.; Kurtz, S.R.
Photocurrent-voltage and long-term stability (greater than a year) results of thin-film Cd(Se,Te)\\/aqueous polysulfide photoelectrochemical solar cells (PEC) are presented. In outdoor experiments, it is demonstrated that small modifications of polysulfide electrolyte composition can increase cadmium chalcogenide\\/polysulfide PEC solar cell lifetimes from months to years. After an initial small rise and fall in solar to electrical conversion efficiency, a photoelectrochemical solar
Materials refining for solar cell silicon
NASA Astrophysics Data System (ADS)
Metallurgical refining processes for the production of solar cell silicon are described. The aim is to obtain an optimum purification effect with a minimum of process steps. The characterization of refined silicon is limited to chemical purity and its correlation with solar quality. Hydrometallurgical refining and pyrometallurgical refining (liquid-liquid extraction, liquid-gas extraction, and recrystallization in aluminum) are treated.
Dietl, J.
Indium oxide/n-silicon heterojunction solar cells
A high photo-conversion efficiency indium oxide/n-silicon heterojunction solar cell is spray deposited from a solution containing indium trichloride. The solar cell exhibits an Air Mass One solar conversion efficiency in excess of about 10%.
Feng, Tom (Morris Plains, NJ); Ghosh, Amal K. (New Providence, NJ)
Solar cell anomaly detection method and apparatus
NASA Technical Reports Server (NTRS)
A method is provided for detecting cracks and other imperfections in a solar cell, which includes scanning a narrow light beam back and forth across the cell in a raster pattern, while monitoring the electrical output of the cell to find locations where the electrical output varies significantly. The electrical output can be monitored on a television type screen containing a raster pattern with each point on the screen corresponding to a point on the solar cell surface, and with the brightness of each point on the screen corresponding to the electrical output from the cell which was produced when the light beam was at the corresponding point on the cell. The technique can be utilized to scan a large array of interconnected solar cells, to determine which ones are defective.
Miller, Emmett L. (Inventor); Shumka, Alex (Inventor); Gauthier, Michael K. (Inventor)
Concepts of learning and experience in developing solar thermal technologies
This study presents a picture of development of solar thermal technology, using the learning and experience curve concepts. The cost estimates for solar thermal energy technologies are made assuming a fixed production process, characterized by standard capacity factors, overhead, and labor costs. The learning curve is suggested as a generalization of the costs of potential solar energy system. The concept
F Krawiec
Radiation Damage Workshop report. [solar cells
NASA Technical Reports Server (NTRS)
The starting material, cell design/geometry, and cell processing/fabrication for silicon and gallium arsenide solar cells are addressed with reference to radiation damage. In general, it is concluded that diagnostic sensitivities and material purities are basic to making significant gains in end-of-life performance and thermal annealability. Further, GaAs material characterization is so sketchy that a well defined program to evaluate such material for solar cell application is needed to maximize GaAs cell technology benefits.
Rahilly, W. P.
High-efficiency solar-cell design modeling
NASA Technical Reports Server (NTRS)
Comprehensive computer models were developed to simulate single junction and multiple junction silicon solar cell structures. The following phenomena submodels were incorporated into computer models: effects due to temperature, impurities, defect energy levels, high injection, and surface states; front surface field, back surface field; oxide charged insulator; carrier confinement; bandgap narrowing; depletion region recombination; series resistance; metal contact shadowing; and anti-reflective coatings. Fabrication of 2 cm x 2 cm n(+)p and n(+)pp(+) near optimized silicon solar cells was done. The cells were characterized with respect to V(oc), 1(sc), P(mp), 1(mp), and eta over the temperature 25 C to 150 C. The accuracy of the computer modeling and correct phenomena submodels and/or analysis were assessed to obtain better than 5% agreement with experimental data. Phenomena that give rise to solar cell losses, were determined and quantified through analysis and experiments.
Lamorte, M. F.
Towards high performance inverted polymer solar cells
NASA Astrophysics Data System (ADS)
Bulk heterojunction polymer solar cells that can be fabricated by solution processing techniques are under intense investigation in both academic institutions and industrial companies because of their potential to enable mass production of flexible and cost-effective alternative to silicon-based electronics. Despite the envisioned advantages and recent technology advances, so far the performance of polymer solar cells is still inferior to inorganic counterparts in terms of the efficiency and stability. There are many factors limiting the performance of polymer solar cells. Among them, the optical and electronic properties of materials in the active layer, device architecture and elimination of PEDOT:PSS are the most determining factors in the overall performance of polymer solar cells. In this presentation, I will present how we approach high performance of polymer solar cells. For example, by developing novel materials, fabrication polymer photovoltaic cells with an inverted device structure and elimination of PEDOT:PSS, we were able to observe over 8.4% power conversion efficiency from inverted polymer solar cells.
Gong, Xiong
Large area polymer solar cells
NASA Astrophysics Data System (ADS)
The fabrication of very large area polymer based solar cell modules with a total aperture area of 1000 cm2 has been accomplished. The substrate was polyethyleneterephthalate (PET) foil with a pre-etched pattern of indium-tin-oxide (ITO) anodes. The module was constructed as a matrix of 91 devices comprising 7 rows connected in parallel with each row having 13 individual cells connected in series. The printing of the organic layer employed screen printing of a chlorobenzene solution of the active material that consisted of either poly-1,4-(2-methoxy-5-ethylhexyloxy) phenylenevinylene (MEH-PPV) on its own or a 1:1 mixture (w/w) of MEH-PPV and [6,6]-phenyl-C61-butanoic acid methyl ester (PCBM). Our first results employed e-beam evaporation of the aluminium cathode directly onto the active layer giving devices with very poor performance that was discouragingly lower than expected by about three orders of magnitude. We found that e-beam radiation leads to a much poorer performance and thermal evaporation of the aluminium using a basket heater improved these values by an order of magnitude in efficiency for the geometry ITO/MEH-PPV/C60/Al. Finally the lifetimes (?1/2) of the modules were established and were found to improve significantly when a sublimed layer of C60 was included between the polymer and the aluminium electrode. Values for the half life of 150 hours were typically obtained. This short lifetime is linked to reaction between the reactive metal electrode (aluminium) and the constituents of the active layer.
Krebs, Frederik C.; Alstrup, Jan; Biancardo, Matteo; Spanggaard, Holger
Contact formation in gallium arsenide solar cells
NASA Technical Reports Server (NTRS)
Gold and gold-based alloys, commonly used as solar cell contact materials, are known to react readily with gallium arsenide. Experiments were performed to identify the mechanisms involved in these GaAs-metal interactions. It is shown that the reaction of GaAs with gold takes place via a dissociative diffusion process. It is shown further that the GaAs-metal reaction rate is controlled to a very great extent by the condition of the free surface of the contact metal, an interesting example of which is the previously unexplained increase in the reaction rate that has been observed for samples annealed in a vacuum environment as compared to those annealed in a gaseous ambient. A number of other hard-to-explain observations, such as the low-temperature formation of voids in the gold lattice and crystallite growth on the gold surface, are explained by invoking this mechanism.
Weizer, Victor G.; Fatemi, Navid S.
Status of silicon solar cell technology
NASA Technical Reports Server (NTRS)
It is pointed out that during the time from 1970 to 1976 the efficiency of solar cells has increased from 10.5 to 15.5%. Most of the increased output has resulted from increased short circuit current. Advances leading to this improvement in performance are discussed, taking into account a reduction in the area covered by the grid pattern, the use of antireflection coatings, and the employment of surface texturizing. A widespread use of solar cells for nonspace applications requires a reduction in the cost of solar cell arrays from the present $20 per watt to 10 to 50 cents per watt. Approaches for achieving this objective are considered. Attention is given to an automated, high volume production of solar cells made from ribbon silicon or thin film layers.
Brandhorst, H. W., Jr.
Perovskite solar cells: Continuing to soar
NASA Astrophysics Data System (ADS)
The dream of printing highly efficient solar cells is closer than ever to being realized. Solvent engineering has enabled the deposition of uniform perovskite semiconductor films that yield greater than 15% power-conversion efficiency.
McGehee, Michael D.
Texturization of multicrystalline silicon solar cells
A significant efficiency gain for crystalline silicon solar cells can be achieved by surface texturization. This research was directed at developing a low-cost, high-throughput and reliable texturing method that can create ...
Li, Dai-Yin
Solar array module plasma interactions experiment (SAMPIE) - Science and technology objectives
NASA Technical Reports Server (NTRS)
The solar array module plasma interactions experiment (SAMPIE) is an approved NASA flight experiment manifested for Shuttle deployment in early 1994. The SAMPIE experiment is designed to investigate the interaction of high voltage space power systems with ionospheric plasma. To study the behavior of solar cells, a number of solar cell coupons (representing design technologies of current interest) will be biased to high voltages to measure both arcing and current collection. Various theories of arc suppression will be tested by including several specially modified cell coupons. Finally, SAMPIE will include experiments to study the basic nature of arcing and current collection. This paper describes the rationale for a space flight experiment, the measurements to be made, and the significance of the expected results. A future paper will present a detailed discussion of the engineering design.
Hillard, G. B.; Ferguson, Dale C.
Status of GaAs solar cell production
NASA Technical Reports Server (NTRS)
Recent experience in producing GaAs solar cells, to meet the full requirements of space-array manufacturers is reviewed. The main problems have been in extending MOCVD technology to provide high throughput of high quality epitaxial layers, and to integrate the other important factors needed to meet the full range of user requirements. Some discussion of evolutionary changes is also given.
Yeh, Milton; Ho, Frank; Iles, Peter A.
Low temperature surface passivation for silicon solar cells
Surface passivation at low processing temperatures becomes an important topic for cheap solar cell processing. In this study, we first give a broad overview of the state of the art in this field. Subsequently, the results of a series of mutually related experiments are given about surface passivation with direct Plasma Enhanced Chemical Vapour Deposition (PECVD) of silicon oxide (Si-oxide)
C. Leguijt; P. L�lgen; J. A. Eikelboom; A. W. Weeber; F. M. Schuurmans; W. C. Sinke; P. F. A. Alkemade; P. M. Sarro; C. H. M. Mar�e; L. A. Verhoef
Monolithic solar cell panel of amorphous silicon
A monolithic solar cell panel has been fabricated using hydrogenated amorphous silicon (a-Si:H) as the semiconductor material. This device consists of a plate glass substrate bearing a number of long, narrow, parallel cells electrically connected in series along the lengths of the cells. It features several characteristics which make it uniquely attractive for large area devices (up to several sq
J. J. Hanak
Composite solar cell matrix is reliable, lightweight and flexible
NASA Technical Reports Server (NTRS)
Conducting strips mechanically and electrically connect individual solar cells into a linear array of cells, called a solar submodule, and then connect in series two or more submodules to form a solar cell matrix. Tiny perforations in the strip make it easy to solder them directly to the individual solar cells.
Yasui, R. K.
Space solar cells: High efficiency and radiation damage
NASA Technical Reports Server (NTRS)
The progress and status of efforts to increase the end-of-life efficiency of solar cells for space use is assessed. High efficiency silicon solar cells, silicon solar cell radiation damage, GaAs solar cell performance and radiation damage and 30 percent devices are discussed.
Brandhorst, H., Jr.; Bernatowicz, D. T.
Criteria for Choice of Material for Building Organic Solar Cells
Organic solar cells, which are a promising low cost alternative to inorganic solar cells, offer a seemingly unlimited choice of material with which one can build the devices. In this talk, the physics of operation of organic solar cells will be explained, bringing out its distinctiveness with respect to that for the traditional inorganic solar cells. Based on this, the
S. Sundar Kumariyer; Kumar Iyer
High-temperature Solar Cell Development
NASA Technical Reports Server (NTRS)
The vast majority of space probes to date have relied upon photovoltaic power generation. If future missions designed to probe environments close to the sun (Figure 1) will be able to use such power generation, solar cells that can function at high temperatures, under high light intensity, and high radiation conditions must be developed. The significant problem is that solar cells lose performance at high temperatures.
Landis, Geoffrey A.; Merritt, Danielle; Raffaelle, Ryne P.; Scheiman, David
Nanowire dye-sensitized solar cells
Excitonic solar cells-including organic, hybrid organic-inorganic and dye-sensitized cells (DSCs)-are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient and stable excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport,
Matt Law; Lori E. Greene; Justin C. Johnson; Richard Saykally; Peidong Yang
Comparative values of advanced space solar cells
NASA Technical Reports Server (NTRS)
A methodology for deriving a first order dollar value estimate for advanced solar cells which consists of defining scenarios for solar array production and launch to orbit and the associated costs for typical spacecraft, determining that portion affected by cell design and performance and determining the attributable cost differences is presented. Break even values are calculated for a variety of cells; confirming that efficiency and related effects of radiation resistance and temperature coefficient are major factors; array tare mass, packaging and packing factor are important; but cell mass is of lesser significance. Associated dollar values provide a means of comparison.
Slifer, L. W., Jr.
Telescience operations with the solar array module plasma interaction experiment
NASA Technical Reports Server (NTRS)
The Solar Array Module Plasma Interactions Experiment (SAMPIE) is a flight experiment that flew on the Space Shuttle Columbia (STS-62) in March 1994, as part of the OAST-2 mission. The overall objective of SAMPIE was to determine the adverse environmental interactions within the space plasma of low earth orbit (LEO) on modern solar cells and space power system materials which are artificially biased to high positive and negative direct current (DC) voltages. The two environmental interactions of interest included high voltage arcing from the samples to the space plasma and parasitic current losses. High voltage arcing can cause physical damage to power system materials and shorten expected hardware life. parasitic current losses can reduce power system efficiency because electric currents generated in a power system drain into the surrounding plasma via parasitic resistance. The flight electronics included two programmable high voltage DC power supplies to bias the experiment samples, instruments to measure the surrounding plasma environment in the STS cargo bay, and the on-board data acquisition system (DAS). The DAS provided in-flight experiment control, data storage, and communications through the Goddard Space Flight Center (GSFC) Hitchhiker flight avionics to the GSFC Payload Operations Control Center (POCC). The DAS and the SAMPIE POCC computer systems were designed for telescience operations; this paper will focus on the experiences of the SAMPIE team regarding telescience development and operations from the GSFC POCC during STS-62. The SAMPIE conceptual development, hardware design, and system verification testing were accomplished at the NASA Lewis Research Center (LeRC). SAMPIE was developed under the In-Space Technology Experiment Program (IN-STEP), which sponsors NASA, industry, and university flight experiments designed to enable and enhance space flight technology. The IN-STEP Program is sponsored by the Office of Space Access and Technology (OSAT).
Wald, Lawrence W.; Bibyk, Irene K.
Manufacture of Solar Cells on the Moon
NASA Technical Reports Server (NTRS)
In support of the space exploration initiative a new architecture for the production of solar cells on the lunar surface is devised. The paper discusses experimental data on the fabrication and properties of lunar glass substrates, evaporated lunar regolith thin film (antireflect coatings and insulators), and preliminary attempts in the fabrication of thin film (silicon/II-VI) photovoltaic materials on lunar regolith substrates. A conceptual design for a solar powered robotic rover capable of fabricating solar cells directly on the lunar surface is provided. Technical challenges in the development of such a facility and strategies to alleviate perceived difficulties are discussed. Finally, preliminary cost benefit ratio analysis for different in situ solar cell production scenarios (using exclusively in-situ planetary resources or hybrid) are discussed.
Freundich, Alex; Ignatiev, Alex; Horton, Charles; Duke, Mike; Curren, Peter; Sibille, Laurent
Nanoscale Charge Transport in Excitonic Solar Cells
Excitonic solar cells, including all-organic, hybrid organic-inorganic and dye-sensitized solar cells (DSSCs), offer strong potential for inexpensive and large-area solar energy conversion. Unlike traditional inorganic semiconductor solar cells, where all the charge generation and collection processes are well understood, these excitonic solar cells contain extremely disordered structures with complex interfaces which results in large variations in nanoscale electronic properties and has a strong influence on carrier generation, transport, dissociation and collection. Detailed understanding of these processes is important for fabrication of highly efficient solar cells. Efforts to improve efficiency are underway at a large number of research groups throughout the world focused on inorganic and organic semiconductors, photonics, photophysics, charge transport, nanoscience, ultrafast spectroscopy, photonics, semiconductor processing, device physics, device structures, interface structure etc. Rapid progress in this multidisciplinary area requires strong synergetic efforts among researchers from diverse backgrounds. Such effort can lead to novel methods for development of new materials with improved photon harvesting and interfacial treatments for improved carrier transport, process optimization to yield ordered nanoscale morphologies with well defined electronic structures.
Venkat Bommisetty, South Dakota State University
Advanced Solar Cells for Satellite Power Systems
NASA Technical Reports Server (NTRS)
The multiple natures of today's space missions with regard to operational lifetime, orbital environment, cost and size of spacecraft, to name just a few, present such a broad range of performance requirements to be met by the solar array that no single design can suffice to meet them all. The result is a demand for development of specialized solar cell types that help to optimize overall satellite performance within a specified cost range for any given space mission. Historically, space solar array performance has been optimized for a given mission by tailoring the features of silicon solar cells to account for the orbital environment and average operating conditions expected during the mission. It has become necessary to turn to entirely new photovoltaic materials and device designs to meet the requirements of future missions, both in the near and far term. This paper will outline some of the mission drivers and resulting performance requirements that must be met by advanced solar cells, and provide an overview of some of the advanced cell technologies under development to meet them. The discussion will include high efficiency, radiation hard single junction cells; monolithic and mechanically stacked multiple bandgap cells; and thin film cells.
Flood, Dennis J.; Weinberg, Irving
Nanoparticle Solar Cell Final Technical Report
The purpose of this work was to demonstrate all-inorganic nanoparticle-based solar cells with photovoltaic performance extending into the near-IR region of the solar spectrum as a pathway towards improving power conversion efficiencies. The field of all-inorganic nanoparticle-based solar cells is very new, with only one literature publication in the prior to our project. Very little is understood regarding how these devices function. Inorganic solar cells with IR performance have previously been fabricated using traditional methods such as physical vapor deposition and sputtering, and solution-processed devices utilizing IR-absorbing organic polymers have been investigated. The solution-based deposition of nanoparticles offers the potential of a low-cost manufacturing process combined with the ability to tune the chemical synthesis and material properties to control the device properties. This work, in collaboration with the Sue Carter research group at the University of California, Santa Cruz, has greatly expanded the knowledge base in this field, exploring multiple material systems and several key areas of device physics including temperature, bandgap and electrode device behavior dependence, material morphological behavior, and the role of buffer layers. One publication has been accepted to Solar Energy Materials and Solar Cells pending minor revision and another two papers are being written now. While device performance in the near-IR did not reach the level anticipated at the beginning of this grant, we did observe one of the highest near-IR efficiencies for a nanoparticle-based solar cell device to date. We also identified several key parameters of importance for improving both near-IR performance and nanoparticle solar cells in general, and demonstrated multiple pathways which showed promise for future commercialization with further research.
Breeze, Alison, J; Sahoo, Yudhisthira; Reddy, Damoder; Sholin, Veronica; Carter, Sue
Development and fabrication of a solar cell junction processing system
NASA Technical Reports Server (NTRS)
A processing system capable of producing solar cell junctions by ion implantation followed by pulsed electron beam annealing was developed and constructed. The machine was to be capable of processing 4-inch diameter single-crystal wafers at a rate of 10(7) wafers per year. A microcomputer-controlled pulsed electron beam annealer with a vacuum interlocked wafer transport system was designed, built and demonstrated to produce solar cell junctions on 4-inch wafers with an AMI efficiency of 12%. Experiments showed that a non-mass-analyzed (NMA) ion beam could implant 10 keV phosphorous dopant to form solar cell junctions which were equivalent to mass-analyzed implants. A NMA ion implanter, compatible with the pulsed electron beam annealer and wafer transport system was designed in detail but was not built because of program termination.
Plastic Schottky-barrier solar cells
A photovoltaic cell structure is fabricated from an active medium including an undoped polyacetylene, organic semiconductor. When a film of such material is in rectifying contact with a metallic area electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates a magnesium layer on the undoped polyacetylene film. With the proper selection and location of elements a photovoltaic cell structure and solar cell are obtained.
Waldrop, J.R.; Cohen, M.J.
Progress in quantum well solar cells
A quantum well solar cell is a special multiple-band gap device with intermediate properties between heterojunction cells (sum of the currents generated in the different materials but voltage controlled by the lowest of the two band gaps) and tandem cells (sum of the voltages but current determined by the worst of the two sub-cells).Strain-balanced GaAsP\\/InGaAs multi-quantum wells move the absorption
M. Mazzer; K. W. J. Barnham; I. M. Ballard; A. Bessiere; A. Ioannides; D. C. Johnson; M. C. Lynch; T. N. D. Tibbits; J. S. Roberts; G. Hill; C. Calder
High voltage planar multijunction solar cell
NASA Technical Reports Server (NTRS)
A high voltage multijunction solar cell is provided wherein a plurality of discrete voltage generating regions or unit cells are formed in a single generally planar semiconductor body. The unit cells are comprised of doped regions of opposite conductivity type separated by a gap or undiffused region. Metal contacts connect adjacent cells together in series so that the output voltages of the individual cells are additive. In some embodiments, doped field regions separated by a overlie the unit cells but the cells may be formed in both faces of the wafer.
Evans, J. C., Jr.; Chai, A. T.; Goradia, C. P. (inventors)
Advanced Modelling of Silicon Wafer Solar Cells
NASA Astrophysics Data System (ADS)
Modelling of solar cells today is general practice in research and widely-used in industry. Established modelling software is typically limited to one dimension and/or to small scales. Additionally, novel effects, like, e.g., the use of diffractive structures or luminescent materials, are not established. In this paper we discuss how the combination of different modelling techniques can be used to overcome these limitations. In this context two examples are presented. The first example concerns the combination of the open source simulation software PC1D with circuit modelling to investigate the effect of local shunts on the global characteristics of a silicon wafer solar cell. For the investigated example (4.5 cm2 cell area) we find that a local point shunt reduces the solar cell efficiency by 4% relative. The second example concerns the modelling of diffractive gratings for thin silicon wafer solar cells. For this purpose, we use the rigorous coupled wave analysis to simulate Sentaurus technical computer-aided design (TCAD) is combined with the rigorous coupled wave analysis, a method to solve Maxwell's equations for periodic structures. Here we show that a grating can be used to improve the absorption in a thin silicon wafer solar cell considerably.
Peters, Marius; Fajun, Ma; Siyu, Guo; Hoex, Bram; Blaesi, Benedikt; Glunz, Stefan; Aberle, Armin; Luther, Joachim
Developing an Advanced Module for Back-Contact Solar Cells
This paper proposes a novel concept for integrating ultrathin solar cells into modules. It is conceived as a method for fabricating solar panels starting from back-contact crystalline silicon solar cells. However, compared to the current state of the art in module manufacturing for back-contact solar cells, this novel concept aims at improvements in performance, reliability, and cost through the use
Jonathan Govaerts; Jo Robbelein; Mario Gonzalez; Ivan Gordon; Kris Baert; Ingrid De Wolf; Frederick Bossuyt; Steven Van Put; Jan Vanfleteren
Third Working Meeting on Gallium Arsenide Solar Cells
NASA Technical Reports Server (NTRS)
Research results are reported for GaAs Schottky barrier solar cells, GaAlAs/GaAs heteroface solar cells, and GaAlAs graded band gap solar cells. Related materials studies are presented. A systems study for GaAs and Si solar concentrator systems is given.
Walker, G. H. (compiler)
Mechanically stacked concentrator tandem solar cells
NASA Technical Reports Server (NTRS)
Four-terminal mechanically stacked solar cells were developed for advanced space arrays with line-focus reflective concentrators. The top cells are based on AlGaAs/GaAs multilayer heterostructures prepared by low temperature liquid phase epitaxy. The bottom cells are based on heteroepitaxial InP/InGaAs liquid phase epitaxy or on homo-junction GaSb, Zn-diffused structures. The sum of the highest reached efficiencies of the top and bottom cells is 29.4 percent. The best four-terminal tandems have an efficiency of 27 to 28 percent. Solar cells were irradiated with 1 MeV electrons and their performances were determined as a function of fluence up to 10(exp 16) cm(exp-2). It was shown that the radiation resistance of developed tandem cells is similar to the most radiative stable AlGaAs/GaAs cells with a thin p-GaAs photoactive layer.
Andreev, V. M.; Rumyantsev, V. D.; Karlina, L. B.; Kazantsev, A. B.; Khvostikov, V. P.; Shvarts, M. Z.; Sorokina, S. V.
Optical designs for improved solar cell performance
NASA Astrophysics Data System (ADS)
The solar resource is the most abundant renewable resource on earth, yet it is currently exploited with relatively low efficiencies. To make solar energy more affordable, we can either reduce the cost of the cell or increase the efficiency with a similar cost cell. In this thesis, we consider several different optical approaches to achieve these goals. First, we consider a ray optical model for light trapping in silicon microwires. With this approach, much less material can be used, allowing for a cost savings. We next focus on reducing the escape of radiatively emitted and scattered light from the solar cell. With this angle restriction approach, light can only enter and escape the cell near normal incidence, allowing for thinner cells and higher efficiencies. In Auger-limited GaAs, we find that efficiencies greater than 38% may be achievable, a significant improvement over the current world record. To experimentally validate these results, we use a Bragg stack to restrict the angles of emitted light. Our measurements show an increase in voltage and a decrease in dark current, as less radiatively emitted light escapes. While the results in GaAs are interesting as a proof of concept, GaAs solar cells are not currently made on the production scale for terrestrial photovoltaic applications. We therefore explore the application of angle restriction to silicon solar cells. While our calculations show that Auger-limited cells give efficiency increases of up to 3% absolute, we also find that current amorphous silicion-crystalline silicon heterojunction with intrinsic thin layer (HIT) cells give significant efficiency gains with angle restriction of up to 1% absolute. Thus, angle restriction has the potential for unprecedented one sun efficiencies in GaAs, but also may be applicable to current silicon solar cell technology. Finally, we consider spectrum splitting, where optics direct light in different wavelength bands to solar cells with band gaps tuned to those wavelengths. This approach has the potential for very high efficiencies, and excellent annual power production. Using a light-trapping filtered concentrator approach, we design filter elements and find an optimal design. Thus, this thesis explores silicon microwires, angle restriction, and spectral splitting as different optical approaches for improving the cost and efficiency of solar cells.
Kosten, Emily Dell
Microstructural analysis of solar cell welds
NASA Astrophysics Data System (ADS)
Parallel-gap resistance welding of silicon solar cells with copper interconnects results in complex microstructural variations that depend on the welding variables. At relatively low heat input solid-state welds are produced. At medium heat the Ag-Cu eutectic forms resulting in a braze joint. High heat produces a fusion weld with complete melting of the silver layer on the silicon solar cell. If the silicon is also melted, cracking occurs in the silicon cell below the weld nugget. These determinations were made using light microscopy, microprobe, and scanning electron microscopy analyses.
Moore, T. J.; Watson, G. K.; Baraona, C. R.
Microstructural analysis of solar cell welds
NASA Technical Reports Server (NTRS)
Parallel-gap resistance welding of silicon solar cells with copper interconnects results in complex microstructural variations that depend on the welding variables. At relatively low heat input solid-state welds are produced. At medium heat the Ag-Cu eutectic forms resulting in a braze joint. High heat produces a fusion weld with complete melting of the silver layer on the silicon solar cell. If the silicon is also melted, cracking occurs in the silicon cell below the weld nugget. These determinations were made using light microscopy, microprobe, and scanning electron microscopy analyses.
Moore, T. J.; Watson, G. K.; Baraona, C. R.
Radiation tests of SEP solar cells
NASA Technical Reports Server (NTRS)
Solar cells specially designed for Solar Electric Propulsion (SEP) were tested with radiation fluences up to 10 to the 12th power protons having energies of 1.5, 1.0, and 0.5 MeV, and with fluences up to 10 to the 16th power electrons having 1.0 MeV energy. Spectrolab cells having a back-surface field were also irradiated with the same particles and fluences. Cell performances are described by curves in which normalized and absolute values of maximum power, maximum-power voltage, short-circuit current, and open-circuit voltage are plotted as a function of fluence.
Oman, H.
Solar Cells in the School Physics Laboratory.
ERIC Educational Resources Information Center
Discusses the goals of experiments which show examples of the use of solar energy on a scale suitable for a school laboratory. Highlights the history of discoveries and developments in photoelectricity. Presents investigations and experiments, that can be performed by students. (JRH)
Mikulski, Kazimeirz
Solar cell calibration and measurement techniques
The increasing complexity of space power solar cells and the increasing international markets for both cells and arrays has resulted in workshops jointly sponsored by NASDA, ESA and NASA. These workshops are designed to obtain international agreement on standardized values for the AM0 spectrum and constant, recommend laboratory measurement practices and establish a set of protocols for international comparison of
Sheila Bailey; Dave Brinker; Henry Curtis; Phillip Jenkins; D. Scheiman
Method of restoring degraded solar cells
Amorphous silicon solar cells have been shown to have efficiencies which degrade as a result of long exposure to light. Annealing such cells in air at a temperature of about 200.degree. C. for at least 30 minutes restores their efficiency.
Staebler, David L. (Lawrenceville, NJ)
Photovoltaic solar cells performance at elevated temperatures
It is well known that efficiency of photovoltaic solar cells decreases with an increase of temperature, and cooling is necessary at high illumination conditions such as concentrated sunlight, or cosmic or tropical conditions. The purpose of present study was to investigate the opposite option: to make a cell work at relatively high temperature (around 100�200 �C) and use the excessive
David Meneses-Rodr??guez; Paul P. Horley; Jes�s Gonz�lez-Hern�ndez; Yuri V. Vorobiev; Peter N. Gorley
Solar Cell Calibration and Measurement Techniques
NASA Technical Reports Server (NTRS)
The increasing complexity of space solar cells and the increasing international markets for both cells and arrays has resulted in workshops jointly sponsored by NASDA, ESA and NASA. These workshops are designed to obtain international agreement on standardized values for the AMO spectrum and constant, recommend laboratory measurement practices and establish a set of protocols for international comparison of laboratory measurements. A working draft of an ISO standard, WDI 5387, 'Requirements for Measurement and Calibration Procedures for Space Solar Cells' was discussed with a focus on the scope of the document, a definition of primary standard cell, and required error analysis for all measurement techniques. Working groups addressed the issues of Air Mass Zero (AMO) solar constant and spectrum, laboratory measurement techniques, and the international round robin methodology. A summary is presented of the current state of each area and the formulation of the ISO document.
Bailey, Sheila; Brinker, Dave; Curtis, Henry; Jenkins, Phillip; Scheiman, Dave
Silicon solar cell process. Development, fabrication and analysis
NASA Technical Reports Server (NTRS)
Solar cells were fabricated from unconventional silicon sheets, and the performances were characterized with an emphasis on statistical evaluation. A number of solar cell fabrication processes were used and conversion efficiency was measured under AMO condition at 25 C. Silso solar cells using standard processing showed an average efficiency of about 9.6%. Solar cells with back surface field process showed about the same efficiency as the cells from standard process. Solar cells from grain boundary passivation process did not show any improvements in solar cell performance.
Yoo, H. I.; Iles, P. A.; Tanner, D. P.
Nanoplasmonics: a frontier of photovoltaic solar cells
NASA Astrophysics Data System (ADS)
Nanoplasmonics recently has emerged as a new frontier of photovoltaic research. Noble metal nanostructures that can concentrate and guide light have demonstrated great capability for dramatically improving the energy conversion efficiency of both laboratory and industrial solar cells, providing an innovative pathway potentially transforming the solar industry. However, to make the nanoplasmonic technology fully appreciated by the solar industry, key challenges need to be addressed; including the detrimental absorption of metals, broadband light trapping mechanisms, cost of plasmonic nanomaterials, simple and inexpensive fabrication and integration methods of the plasmonic nanostructures, which are scalable for full size manufacture. This article reviews the recent progress of plasmonic solar cells including the fundamental mechanisms, material fabrication, theoretical modelling and emerging directions with a distinct emphasis on solutions tackling the above-mentioned challenges for industrial relevant applications.
Gu, Min; Ouyang, Zi; Jia, Baohua; Stokes, Nicholas; Chen, Xi; Fahim, Narges; Li, Xiangping; Ventura, Michael James; Shi, Zhengrong
Black silicon for solar cell applications
NASA Astrophysics Data System (ADS)
We present experimental results and rigorous numerical simulations on the optical properties of Black Silicon surfaces and their implications for solar cell applications. The Black Silicon is fabricated by reactive ion etching of crystalline silicon with SF6 and O2. This produces a surface consisting of sharp randomly distributed needle like features with a characteristic lateral spacing of about a few hundreds of nanometers and a wide range of aspect ratios depending on the process parameters. Due to the very low reflectance over a broad spectral range and a pronounced light trapping effect at the silicon absorption edge such Black Silicon surface textures are beneficial for photon management in photovoltaic applications. We demonstrate that those light trapping properties prevail upon functionalization of the Black Silicon with dielectric coatings, necessary to construct a photovoltaic system. The experimental investigations are accompanied by rigorous numerical simulations based on three dimensional models of the Black Silicon structures. Those simulations allow insights into the light trapping mechanism and the influence of the substrate thickness onto the optical performance of the Black Silicon. Finally we use an analytical solar cell model to relate the optical properties of Black Silicon to the maximum photo current and solar cell efficiency in dependence of the solar cell thickness. The results are compared to standard light trapping schemes and implications especially for thin solar cells are discussed.
Kroll, Matthias; Otto, Martin; K�sebier, Thomas; F�chsel, Kevin; Wehrspohn, Ralf; Kley, Ernst-Bernhard; T�nnermann, Andreas; Pertsch, Thomas
Nanocluster production for solar cell applications
NASA Astrophysics Data System (ADS)
This research focuses on the fabrication and characterization of silver (Ag) and silicon (Si) nanoclusters that might be used for solar cell applications. Silver and silicon nanoclusters have been synthesized by means of dc magnetron sputtering and inert gas condensation inside an ultra-high vacuum compatible system. We have found that nanocluster size distributions can be tuned by various source parameters, such as the sputtering discharge power, flow rate of argon inert gas, and aggregation length. Quadrupole mass filter and transmission electron microscopy were used to evaluate the size distribution of Ag and Si nanoclusters. Ag nanoclusters with average size in the range of 3.6-8.3 nm were synthesized (herein size refers to the nanocluster diameter), whereas Si nanoclusters' average size was controlled to range between 2.9 and 7.4 nm by controlling the source parameters. This work illustrates the ability of controlling the Si and Ag nanoclusters' sizes by proper optimization of the operation conditions. By controlling nanoclusters' sizes, one can alter their surface properties to suit the need to enhance solar cell efficiency. Herein, Ag nanoclusters were deposited on commercial polycrystalline solar cells. Short circuit current (ISC), open circuit voltage (VOC), fill factor, and efficiency (?) were obtained under light source with an intensity of 30 mW/cm2. A 22.7% enhancement in solar cell efficiency could be measured after deposition of Ag nanoclusters, which demonstrates that Ag nanoclusters generated in this work are useful to enhance solar cell efficiency.
Al Dosari, Haila M.; Ayesh, Ahmad I.
Method of fabricating a solar cell array
A first set of pre-tabbed solar cells are assembled in a predetermined array with at least part of each tab facing upward, each tab being fixed to a bonding pad on one cell and abutting a bonding pad on an adjacent cell. The cells are held in place with a first vacuum support. The array is then inverted onto a second vacuum support which holds the tabs firmly against the cell pads they abut. The cells are exposed to radiation to melt and reflow the solder pads for bonding the tab portions not already fixed to bonding pads to these pads.
Lazzery, Angelo G. (Oaklyn, NJ); Crouthamel, Marvin S. (Pennsauken, NJ); Coyle, Peter J. (Oaklyn, NJ)
Electron Radiation Damage of (alga) As-gaas Solar Cells
NASA Technical Reports Server (NTRS)
Solar cells (2 cm by 2 cm (AlGa) As-GaAs cells) were fabricated and then subjected to irradiation at normal incidence by electrons. The influence of junction depth and n-type buffer layer doping level on the cell's resistance to radiation damage was investigated. The study shows that (1) a 0.3 micrometer deep junction results in lower damage to the cells than does a 0.5 micrometer junction, and (2) lowering the n buffer layer doping density does not improve the radiation resistance of the cell. Rather, lowering the doping density decreases the solar cell's open circuit voltage. Some preliminary thermal annealing experiments in vacuum were performed on the (AlGa)As-GaAs solar cells damaged by 1-MeV electron irradiation. The results show that cell performance can be expected to partially recover at 200 C with more rapid and complete recovery occurring at higher temperature. For a 0.5hr anneal at 400 C, 90% of the initial power is recovered. The characteristics of the (AlGa)As-GaAs cells both before and after irradiation are described.
Loo, R.; Kamath, G. S.; Knechtli, R.
High temperature operation of photovoltaic solar cells in one- and two-stage systems
Experimental and theoretical analysis is made of the efficiency of high temperature operation of a photovoltaic solar cell. Experiments were performed With cells made of crystalline Si (c-Si, with gn junction and Shottky barrier), amorphous (a-) Si and CuInSez (CIS) in the temperature interval 25 - 150 'C, using the solar radiation with concentration degree from I to 30. The
David Meneses-Rodriguez; Paul P. Horley; S. A. Kostylev; J. Gonzalez-Hernandez; Y. V. Vorobiev
Summary of solar cell data from the Long Duration Exposure Facility (LDEF)
NASA Technical Reports Server (NTRS)
The contractor has obtained and reviewed data relating solar cells assemblies (SCA's) flown as part of the following LDEF experiments: the Advanced Photovoltaic Experiment (S0014); the Solar Array Materials Passive LDEF Experiment (A0171); the Advanced Solar Cell and Coverglass Analysis Experiment (M0003-4); the LDEF Heat Pipe Experiment (S1001); the Evaluation of Thermal Control Coatings Y Solar Cells Experiment (S1002); and the Space Plasma-High Voltage Drainage Experiment (A0054). Where possible, electrical data have been tabulated and correlated with various environmental effects, including meteoroid and debris impacts, radiation exposure, atomic oxygen exposure, contamination, UV radiation exposure, and thermal cycling. The type, configuration, and location of all SCA's are documented here. By gathering all data and results together, a comparison of the survivability of the various types and configurations can be made.
Hill, David C.; Rose, M. Frank
Development of a large area space solar cell assembly
NASA Technical Reports Server (NTRS)
The development of a large area high efficiency solar cell assembly is described. The assembly consists of an ion implanted silicon solar cell and glass cover. The important attributes of fabrication are the use of a back surface field which is compatible with a back surface reflector, and integration of coverglass application and cell fabrications. Cell development experiments concerned optimization of ion implantation processing of 2 ohm-cm boron-doped silicon. Process parameters were selected based on these experiments and cells with area of 34.3 sq cm wre fabricated. The average AMO efficiency of the twenty-five best cells was 13.9% and the best bell had an efficiency of 14.4%. An important innovation in cell encapsulation was also developed. In this technique, the coverglass is applied before the cell is sawed to final size. The coverglass and cell are then sawed as a unit. In this way, the cost of the coverglass is reduced, since the tolerance on glass size is relaxed, and costly coverglass/cell alignment procedures are eliminated. Adhesive investigated were EVA, FEP-Teflon sheet and DC 93-500. Details of processing and results are reported.
Spitzer, M. B.
Development of irradiation methods and degradation modeling for state-of-the-art space solar cells
NASA Astrophysics Data System (ADS)
Japan Atomic Energy Agency (JAEA) together with Japan Aerospace Exploration Agency (JAXA) has developed an insitu evaluation technique for understanding radiation response of space solar cells, by which the electrical characteristics of solar cells can be measured under AM0 light illumination during proton/electron irradiation experiments (Simultaneous method). Using the simultaneous method, we revealed the radiation degradation of multi-junction solar cells such as InGaP/GaAs/Ge triple junction (3J) solar cells. A modeling of the radiation degradation of 3J solar cells based on the Non-Ionizing Energy Loss (NIEL) concept was established. Flexible multi-junction solar cells are under development for space applications.
Ohshima, Takeshi; Sato, Shin-ichiro; Sumita, Taishi; Nakamura, Tetsuya; Imaizumi, Mitsuru
Nanocrystal-polymer solar cells
The ability to structure materials on a nanometer dimension enables the processes of solar energy conversion to be optimized at their most fundamental length scale. In semiconducting nanocrystals, optical absorption and electrical transport can be tailored by changing their radius and length, respectively. The unique features of quantum confinement and shape manipulation characteristic for inorganic nanocrystals can be utilized to
Wendy Uyen Huynh
Space solar cell research - Problems and potential
NASA Technical Reports Server (NTRS)
The value of a passive, maintenance-free, renewable energy source was immediately recognized in the early days of the space program, and the silicon solar cell, despite its infancy, was quickly pressed into service. Efficiencies of those early space solar arrays were low, and lifetimes shorter than hoped for, but within a decade significant advances had been made in both areas. Better performance was achieved because of a variety of factors, ranging from improvements in silicon single crystal material, to better device designs, to a better understanding of the factors that affect the performance of a solar cell in space. Chief among the latter, particularly for the mid-to-high altitude (HEO) and geosynchronous (GEO) orbits, are the effects of the naturally occurring particulate radiation environment. Although not as broadly important to the photovoltaic community at large as increased efficiency, the topic of radiation damage is critically important to use of solar cells in space, and is a major component of the NASA research program in space photovoltaics. This paper will give a brief overview of some of the opportunities and challenges for space photovoltaic applications, and will discuss some of the current reseach directed at achieving high efficiency and controlling the effects of radiation damage in space solar cells.
Flood, Dennis J.
Space solar cell research: Problems and potential
NASA Technical Reports Server (NTRS)
The value of a passive, maintenance-free, renewable energy source was apparent in the early days of the space program, and the silicon solar cell was pressed into service. Efficiencies of those early space solar arrays were low, and lifetimes shorter than hoped for, but within a decade significant advances had been made in both areas. Better performance was achieved through improvements in silicon single crystal material, better device designs, and a better understanding of the factors that affect the performance of a solar cell in space. Chief among the latter, particularly for the mid-to-high altitude (HEO) and geosynchronous (GEO) orbits, are the effects of the naturally occurring particulate radiation environment. Although not as broadly important to the photovoltaic community at large as increased efficiency, the topic of radiation damage is critically important to use of solar cells in space, and is a major component of the NASA research program in space photovoltaics. A brief overview of some of the opportunities and challenges for space photovoltaic applications is given, and some of the current research directed at achieving high efficiency and controlling radiation damage in space solar cells is discussed.
Flood, D. J.
Large area monolithic organic solar cells
NASA Astrophysics Data System (ADS)
Although efficiencies of > 10% have recently been achieved in laboratory-scale organic solar cells, these competitive performance figures are yet to be translated to large active areas and geometries relevant for viable manufacturing. One of the factors hindering scale-up is a lack of knowledge of device physics at the sub-module level, particularly cell architecture, electrode geometry and current collection pathways. A more in depth understanding of how photocurrent and photovoltage extraction can be optimised over large active areas is urgently needed. Another key factor suppressing conversion efficiencies in large area cells is the relatively high sheet resistance of the transparent conducting anode - typically indium tin oxide. Hence, to replace ITO with alternative transparent conducting anodes is also a high priority on the pathway to viable module-level organic solar cells. In our paper we will focus on large area devices relevant to sub-module scales - 5 cm � 5 cm monolithic geometry. We have applied a range of experimental techniques to create a more comprehensive understanding of the true device physics that could help make large area, monolithic organic solar cells more viable. By employing this knowledge, a novel transparent anode consisting of molybdenum oxide (MoOx) and silver (Ag) is developed to replace ITO and PEDOT-free large area solar cell sub-modules, acting as both a transparent window and hole-collecting electrode. The proposed architecture and anode materials are well suited to high throughput, low cost all-solution processing.
Jin, Hui; Tao, Cheng; Hambsch, Mike; Pivrikas, Almantas; Velusamy, Marappan; Aljada, Muhsen; Zhang, Yuliang; Burn, Paul L.; Meredith, Paul
Solar Neutrino Experiments Neutrinos are ghostlike particles that
#12;Solar Neutrino Experiments Neutrinos are ghostlike particles that were postulated by Wolfgang investigat- ing neutrinos that were produced in Brookhaven's Graphite Research Reactor and at a reactor to Davis's major triumph, which came in the early 1970s, when he successfully de- tected solar neutrinos
Solar Cell Modules with Parallel Oriented Interconnections
NASA Technical Reports Server (NTRS)
Twenty-four solar modules, half of which were 48 cells in an all-series electrical configuration and half of a six parallel cells by eight series cells were provided. Upon delivery of environmentally tested modules, low power outputs were discovered. These low power modules were determined to have cracked cells which were thought to cause the low output power. The cracks tended to be linear or circular which were caused by different stressing mechanisms. These stressing mechanisms were fully explored. Efforts were undertaken to determine the causes of cell fracture. This resulted in module design and process modifications. The design and process changes were subsequently implemented in production.
Design and fabrication of solar cell modules
NASA Technical Reports Server (NTRS)
A program conducted for design, fabrication and evaluation of twelve silicon solar cell modules is described. The purpose of the program was to develop a module design consistent with the requirements and objectives of JPL specification and to also incorporate elements of new technologies under development to meet LSSA Project goals. Module development emphasized preparation of a technically and economically competitive design based upon utilization of ion implanted solar cells and a glass encapsulation system. The modules fabricated, tested and delivered were of nominal 2 X 2 foot dimensions and 20 watt minimum rating. Basic design, design rationale, performance and results of environmental testing are described.
Shaughnessy, T. P.
Solar cell contact formation using laser ablation
The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.
Harley, Gabriel; Smith, David; Cousins, Peter
High throughput solar cell ablation system
A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.
Harley, Gabriel; Pass, Thomas; Cousins, Peter John; Viatella, John
Oxide heterostructures for ecient solar cells
We propose an unexplored class of absorbing materials for high-efficiency solar cells: heterostructures of transition-metal oxides. In particular, LaVO3 grown on SrTiO3 has a direct band gap ~1.1 eV in the optimal range as well as an internal potential gradient, which can greatly help to separate the photogenerated electron-hole pairs. Furthermore, oxide heterostructures afford the flexibility to combine LaVO3 with other materials such as LaFeO3 in order to achieve even higher efficiencies with band-gap graded solar cells. We use density-functional theory to demonstrate these features.
Assmann, E. [Vienna University of Technology, Austria; Blaha, P. [Institute for Materials Chemistry, TU Vienna; Laskowski, R [Institute for Materials Chemistry, TU Vienna; Held, K. [Vienna University of Technology, Austria; Okamoto, Satoshi [ORNL; Sangiovanni, G. [University of Wuerzburg, Germany
Impedance spectroscopic characterization of solar cell
NASA Astrophysics Data System (ADS)
Impedance spectroscopy is used to characterize a commercial solar cell, at various dc bias potentials, under illumination and dark conditions. Interesting features are observed in medium and low frequency range, at large bias potentials. All the models reported in literature utilize combinations of resistances and capacitances, but the results indicate that inductances are necessary to model the actual solar cell, since an inductive loop is observed in the medium frequency range, especially at large bias potential, both under illumination and dark conditions. A new circuit which captures all the trends semi quantitatively is proposed to model the data.
Gautham, S.; Ramanathan, S.
Gaalas/Gaas Solar Cell Process Study
NASA Technical Reports Server (NTRS)
Available information on liquid phase, vapor phase (including chemical vapor deposition) and molecular beam epitaxy growth procedures that could be used to fabricate single crystal, heteroface, (AlGa) As/GaAs solar cells, for space applications is summarized. A comparison of the basic cost elements of the epitaxy growth processes shows that the current infinite melt LPE process has the lower cost per cell for an annual production rate of 10,000 cells. The metal organic chemical vapor deposition (MO-CVD) process has the potential for low cost production of solar cells but there is currently a significant uncertainty in process yield, i.e., the fraction of active material in the input gas stream that ends up in the cell. Additional work is needed to optimize and document the process parameters for the MO-CVD process.
Almgren, D. W.; Csigi, K. I.
NASA Technical Reports Server (NTRS)
The design, fabrication, and characterization of high-performance, n(+)/p InP shallow-homojunction (SHJ) concentrator solar cells are described. The InP device structures were grown by atmospheric-pressure metalorganic vapor phase epitaxy. A preliminary assessment of the effects of grid-collection distance and emitter-sheet resistance on cell performance is presented. At concentration ratios of around 100, cells with efficiencies of 21.4 percent AM0 (24.3 percent direct) at 25 C are fabricated. These are the highest efficiencies yet reported for single-junction InP solar cells. The performance of these cells as a function of temperature is discussed, and areas for future improvement are outlined. Application of these results to other InP-based photovoltaic devices is discussed.
Ward, J. S.; Wanlass, M. W.; Coutts, T. J.; Emery, K. A.; Osterwald, C. R.
NASA Technical Reports Server (NTRS)
Circuit identified malfunctioning photovoltaic array. Cell-failure detection circuit compares output of photovoltaic array to control cell. If any module fails, activates light-emitting diode. Circuit could also sound alarm.
Maloney, T. J.
Multi-junction solar cell device
A multi-junction solar cell device (10) is provided. The multi-junction solar cell device (10) comprises either two or three active solar cells connected in series in a monolithic structure. The multi-junction device (10) comprises a bottom active cell (20) having a single-crystal silicon substrate base and an emitter layer (23). The multi-junction device (10) further comprises one or two subsequent active cells each having a base layer (32) and an emitter layer (23) with interconnecting tunnel junctions between each active cell. At least one layer that forms each of the top and middle active cells is composed of a single-crystal III-V semiconductor alloy that is substantially lattice-matched to the silicon substrate (22). The polarity of the active p-n junction cells is either p-on-n or n-on-p. The present invention further includes a method for substantially lattice matching single-crystal III-V semiconductor layers with the silicon substrate (22) by including boron and/or nitrogen in the chemical structure of these layers.
Friedman, Daniel J. (Lakewood, CO); Geisz, John F. (Wheat Ridge, CO)
Photovoltaic solar cell application for e-book
An embedded systems like e-Book where it consumes less power and employs greatly in outdoor environment, solar energy can be introduced for extending the reading time. In this paper, to design e-book system with photovoltaic solar cell application, solar harvesting module must be considered. But measurement showed that charging current for battery is significantly affected by solar cell type and
Hee-Won Lee; Jong-Soo Kim; Byoung-Kuk Lee
[H�rthle cell tumors: personal experience].
H�rthle cell tumors of the thyroid gland are uncommon lesions (3% of all well differentiated tumors). Histological diagnosis is often difficult: according to recent criteria only those tumors with almost 75% of oxyphil cells are well recognized as H�rthle cell neoplasms. Extracapsular and blood-vessels invasion, capsular penetration, DNA patterns and tumoral necrosis are indicative for malignancy. The Authors report their experience in the management of 46 patients who underwent thyroid surgery for H�rthle cell neoplasms. Histological findings, surgical approach and post-operative follow up are discussed. PMID:7654499
De Toma, G; Gabriele, R; Sgarzini, G; Plocco, M; Campli, M; Sambuco, L
Plastic solar cells with engineered interfaces
NASA Astrophysics Data System (ADS)
We discuss here bulk-heterojunction polymer solar cells with engineered interfaces to achieve desired phase separations (vertical and horizontal), molecule orientations, ohmic contacts, and electronic properties for device performance maximization, and to enhance the device durability by eliminating corrosive interfacial layers. The strategies discussed include development of novel interfacial layers such as self-assembled organic layers and inorganic metal oxide layers, and using inverted cell architectures. Interface engineering leads to optimal active layer morphologies and to polymer ?- orientation, as well as maximum open circuit voltage. Using p-type NiO as the anode hole transporting/electron blocking layer results in dramatically enhanced device performance of P3HT/PCBM polymer solar cells with PCEs up to 5%. Electrical property and surface morphology investigations of NiO elucidate the mechanism for the enhanced performance. Other novel interfacial materials such as self-assembled organic monolayers and graphene oxide (GO) have also been incorporated into polymer solar cells to achieve comparable PCEs with improved device stability. Using ZnO as electron transporting/hole blocking layer and employing an inverted device architecture, polymer solar cells achieve desired molecule ?-orientation and vertical phase separation, therefore extremely high fill factors and promising power conversion efficiencies. In addition to interfacial layer materials, active layer components with state-of-the-art device performance, both polymer and small molecule developed in this laboratory, will also be discussed.
Guo, Xugang; Marks, Tobin J.
MDAC solar cosmic ray experiment on OGO-6
NASA Technical Reports Server (NTRS)
The instrumentation of the OGO-F solar cosmic ray experiment is described and results of data obtained during the satellite lifetime from launch on June 5, 1969, through September, 1970, and discussed.
Masley, A. J.
Solar Energy Experiments for High School and College Students.
ERIC Educational Resources Information Center
This publication contains eighteen experiments and eight classroom activities. The experiments are of varying difficulty and cover the important aspects of solar energy utilization. Each experiment is self-contained, with its own introduction and background information. Energy measurements are emphasized and techniques for collector efficiency�
Norton, Thomas W.; And Others
Electrical overstress failure in silicon solar cells
A solar-cell electrical-overstress-failure model and the results of experimental measurements of threshold pulsed failure currents on four types of silicon solar cells are presented. The transient EMP field surrounding a lightning stroke has been identified as a potential threat to a photovoltaic array, yet failure analysis of solar cells in a pulsed environment had not previously been reported. Failure in the low-resistivity concentrator cells at pulse widths between 1 ..mu..s and 1 ms occurred initially in the junction. Finger damage in the form of silver melting occurs at currents only slightly greater than that required for junction damage. The result of reverse-bias transient-overstress tests on high-resistivity (10 ..cap omega..cm) cells demonstrated that the predominant failure mode was due to edge currents. These flat-plate cells failed at currents of only 4 to 20 A, which is one or two orders of magnitude below the model predictions. It thus appears that high-resistivity flat-plate cells are quite vulnerable to electrical overstress which could be produced by a variety of mechanisms.
Pease, R.L.; Barnum, J.R.; van Lint, V.A.J.; Vulliet, W.V.; Wrobel, T.F.
High-performance silicon nanohole solar cells.
We demonstrate Si nanohole arrays as a superior sunlight-absorbing nanostructure for photovoltaic solar cell applications. Under 1 sun AM1.5G illumination, a Si nanohole solar cell with p-n junctions via P diffusion exhibited a open-circuit voltage of 566.6 mV, a short-circuit current density of 32.2 mA/cm(2), and a remarkable power conversion efficiency of 9.51%, which is higher than that of its counterparts based on Si nanowires, planar Si, and pyramid-textured Si. The nanohole array geometry presents a novel and viable method fo cost-efficient solar energy conversion. PMID:20426468
Peng, Kui-Qing; Wang, Xin; Li, Li; Wu, Xiao-Ling; Lee, Shuit-Tong
Development of economical improved thick film solar cell contact
NASA Technical Reports Server (NTRS)
Metal screened electrodes were investigated with base metal pastes and silver systems being focused upon. Contact resistance measurements were refined. A facility allowing fixing in hydrogen and other atmospheres was acquired. Several experiments were made applying screenable pastes to solar cells. Doping investigations emphasized eutectic alloys reduced to powders. Metal systems were reviewed and base metal experiments were done with nickel and copper using lead and tin as the frit metals. Severe adhesion problems were experienced with hydrogen atmospheres in all metal systems. A two step firing schedule was devised. Aluminum-silicon and aluminum-germanium eutectic doping additions to copper pastes were tried on 2 1/4 in diameter solar cell back contacts, both with good results.
Ross, B.
Cost competitiveness of a solar cell array power source for ATS-6 educational TV terminal
NASA Technical Reports Server (NTRS)
A cost comparison is made between a terrestrial solar cell array power system and a variety of other power sources for the ATS-6 Satellite Instructional Television Experiment (SITE) TV terminals in India. The solar array system was sized for a typical Indian location, Lahore. Based on present capital and fuel costs, the solar cell array power system is a close competitor to the least expensive alternate power system. A feasibility demonstration of a terrestrial solar cell array system powering an ATS-6 receiver terminal at Cleveland, Ohio is described.
Masters, R. M.
High temperature investigations of crystalline silicon solar cell materials
Crystalline silicon solar cells are a promising candidate to provide a sustainable, clean energy source for the future. In order to bring about widespread adoption of solar cells, much work is needed to reduce their cost. ...
Hudelson, George David Stephen, III
Photovoltaic nanocrystal scintillators hybridized on Si solar cells
Photovoltaic nanocrystal scintillators hybridized on Si solar cells for enhanced email@example.com Abstract: We propose and demonstrate semiconductor nanocrystal based photovoltaic scintillators integrated on solar cells to enhance photovoltaic device parameters including spectral responsivity, open circuit
Demir, Hilmi Volkan
Center punched solar cell module development effort
NASA Technical Reports Server (NTRS)
The results are given of an advanced module development program with the objective of providing a low cost solar cell mechanical interconnect design. The design approach, which avoids soldering or welding operations, lends itself to automated assembly techniques thus supporting the Low-Cost Silicon Solar Array Project goals. The first group of six modules contained aluminum contact cells and the second group of six modules contained silver-titanium-palladium contact cells. Extensive component and environmental testing at the module level showed that reliable cell mechanical interconnection can be achieved when utilizing the proper electrical contact materials and pressures. A discussion is given of the module design, manufacturing procedure, test program, significant problem areas and solutions, and conclusions and recommendations as formulated and conducted by XEOS.
Ross, R. E.; Mortensen, W. E.
Studies of silicon pn junction solar cells
NASA Technical Reports Server (NTRS)
Modifications of the basic Shockley equations that result from the random and nonrandom spatial variations of the chemical composition of a semiconductor were developed. These modifications underlie the existence of the extensive emitter recombination current that limits the voltage over the open circuit of solar cells. The measurement of parameters, series resistance and the base diffusion length is discussed. Two methods are presented for establishing the energy bandgap narrowing in the heavily-doped emitter region. Corrections that can be important in the application of one of these methods to small test cells are examined. Oxide-charge-induced high-low-junction emitter (OCI-HLE) test cells which exhibit considerably higher voltage over the open circuit than was previously seen in n-on-p solar cells are described.
Lindholm, F. A.; Neugroschel, A.
Behavior of lithium in irradiated solar cells.
NASA Technical Reports Server (NTRS)
The current state of the art in radiation resistant lithium-doped silicon solar cells is reviewed. Fabrication techniques are reviewed. Characteristics of lithium-doped cells are discussed. Behavior of lithium-doped cells during 1 MeV electron irradiation are studied for various types of cells. Effects of variations in lithium and oxygen concentration are shown and discussed. Capacitance measurements at various voltages, frequencies and temperatures are used to detect charges in lithium donor concentration and the formation of defects during irradiation. Physical models to explain the observed effects are presented.
Carter, J. R., Jr.; Downing, R. G.
Phthalocyanine Blends Improve Bulk Heterojunction Solar Cells
A core phthalocyanine platform allows engineering the solubility properties the band gap; shifting the maximum absorption toward the red. A simple method to increase the efficiency of heterojunction solar cells uses a self-organized blend of the phthalocyanine chromophores fabricated by solution processing. PMID:20136126
Varotto, Alessandro; Nam, Chang-Yong; Radivojevic, Ivana; Tome, Joao; Cavaleiro, Jose A.S.; Black, Charles T.; Drain, Charles Michael
Thick film metallization for solar cell applications
The use of an integral printing technique for the fabrication of silicon solar cells is attractive due to its throughput rate, materials utilization, and modular, automatable design. The transfer of this technology from single crystal to semicrystalline silicon requires a significant amount of process optimization. Processing parameters found to be critical include the optimum glass frit content in the silver-based
G. C. Cheek; R. P. Mertens; R. Van Overstraeten; L. Frisson
Aluminum doping improves silicon solar cells
NASA Technical Reports Server (NTRS)
Aluminum doped silicon solar cells with resistivities in the 10- to 20-ohm centimeter range have broad spectral response, high efficiency and long lifetimes in nuclear radiation environments. Production advantages include low material rejection and increased production yields, and close tolerance control.
Metal electrode for amorphous silicon solar cells
An amorphous silicon solar cell having an N-type region wherein the contact to the N-type region is composed of a material having a work function of about 3.7 electron volts or less. Suitable materials include strontium, barium and magnesium and rare earth metals such as gadolinium and yttrium.
Williams, Richard (Princeton, NJ)
Basic mechanisms governing solar-cell efficiency
NASA Technical Reports Server (NTRS)
The efficiency of a solar cell depends on the material parameters appearing in the set of differential equations that describe the transport, recombination, and generation of electrons and holes. This paper describes the many basic mechanisms occurring in semiconductors that can control these material parameters.
Lindholm, F. A.; Neugroschel, A.; Sah, C. T.
Screen printed interdigitated back contact solar cell
NASA Astrophysics Data System (ADS)
Interdigitated back contact solar cells are made by screen printing dopant materials onto the back surface of a semiconductor substrate in a pair of interdigitated patterns. These dopant materials are then diffused into the substrate to form junctions having configurations corresponding to these patterns. Contacts having configurations which match the patterns are then applied over the junctions.
Baraona, C. R.; Mazaris, G. A.; Chai, A. T.
Screen printed interdigitated back contact solar cell
NASA Technical Reports Server (NTRS)
Interdigitated back contact solar cells are made by screen printing dopant materials onto the back surface of a semiconductor substrate in a pair of interdigitated patterns. These dopant materials are then diffused into the substrate to form junctions having configurations corresponding to these patterns. Contacts having configurations which match the patterns are then applied over the junctions.
Baraona, C. R.; Mazaris, G. A.; Chai, A. T. (inventors)
Limiting Emission Angle for Improved Solar Cell
impact on voltage and efficiency, particularly for cells with high radiative efficiency. In this talk, we cooling, waste heat recovery and solar electricity generation, low values of the thermoelectric figure scattering could lead to new engineering approaches for thermoelectric materials with high zT and new green
Low cost silicon solar cell array
NASA Technical Reports Server (NTRS)
The technological options available for producing low cost silicon solar cell arrays were examined. A project value of approximately $250/sq m and $2/watt is projected, based on mass production capacity demand. Recommendations are included for the most promising cost reduction options.
Bartels, F. T. C.
Sensitized solar cells based on nanostructures
NASA Astrophysics Data System (ADS)
Sensitized solar cells (SSCs) based on nanostructures including dye sensitized solar cells (DSSCs) and quantum dot sensitized solar cells (QDSSCs) have attracted great research interest due to their potential in converting sunlight into electricity and solving the energy problem. Metal oxide nanowires, as an important type of nanostructures were grown and applied in the SSCs. In this dissertation, two types of nanowires, ZnO and Zn2GeO4 nanowires were successfully grown onto fluorine-doped-tin-oxide (FTO) coated substrates using a chemical vapor deposition method. This method provides an important way to grow ZnO nanowires directly on FTO substrates without using any catalyst. ZnO nanowires with length of more than 30 mum were used as the photoanode for DSSCs. The dependence of solar cell performance on nanowire length and annealing temperature was studied. Zn2GeO4 nanowires were also directly synthesized on FTO substrates and were utilized as the photoanode in DSSCs and QDSSCs. Transient photocurrent and photovoltage decay measurements were conducted in the SSCs, which showed that the dye sensitization pH was important for DSSCs and that both the QDs coverage and band alignment between QDs and nanowires were key parameters for QDSSCs in order to have a good energy conversion efficiency.
Lu, Liyou
Amorphous silicon nanocone array solar cell
In the hydrogenated amorphous silicon [a-Si:H]-thin film solar cell, large amounts of traps reduce the carrier's lifetime that limit the photovoltaic performance, especially the power conversion efficiency. The nanowire structure is proposed to solve the low efficiency problem. In this work, we propose an amorphous silicon [a-Si]-solar cell with a nanocone array structure were implemented by reactive-ion etching through a polystyrene nanosphere template. The amorphous-Si nanocone exhibits absorption coefficient around 5 � 105/cm which is similar to the planar a-Si:H layer in our study. The nanostructure could provide the efficient carrier collection. Owing to the better carrier collection efficiency, efficiency of a-Si solar cell was increased from 1.43% to 1.77% by adding the nanocone structure which has 24% enhancement. Further passivation of the a-Si:H surface by hydrogen plasma treatment and an additional 10-nm intrinsic-a-Si:H layer, the efficiency could further increase to 2.2%, which is 54% enhanced as compared to the planar solar cell. The input-photon-to-current conversion efficiency spectrum indicates the efficient carrier collection from 300 to 800 nm of incident light. PMID:22395021
Contacts for semitransparent organic solar cells
The optical absorption in organic solar cells, and hence their efficiency to convert sunlight into electricity, is limited by both a confined spectral absorption range and the very thin active layers which are required since polymers have short charge carrier diffusion lengths. We propose to make the most of this apparent `drawback' by using transparent contacts on both sides of
J. Hanisch; E. Ahlswede; M. Powalla
Amorphous Siliconbased Solar Cells Xunming Deng1
SILICONBASED SOLAR CELLS In Dundee, Scotland, Walter Spear and Peter LeComber discovered around 1973 can induce a significant electrical current through the gas, and the molecules of the gas often emit of America (RCA) Research Laboratory in Princeton, David Carlson discovered that he could make fairly
Schiff, Eric A.
Large area Czochralski silicon for solar cells
NASA Technical Reports Server (NTRS)
A detailed model of a typical Czochralski silicon crystal puller is utilized to predict maximum crystal growth rate as a function of various furnace parameters. Results of this analysis, when combined with multiblade slurry sawing, indicate that the Czochralski process is highly attractive for achieving near-term cost reduction of solar cell silicon.
Rea, S. N.; Wakefield, G. F.
Status of silicon solar cell technology
NASA Technical Reports Server (NTRS)
Major progress in solar cell technology leading to increased efficiency has occurred since 1970. Technical approaches leading to this increased output include surface texturing, improved antireflection coatings, reduced grid pattern area coverage, shallow junctions and back surface fields. The status of these developments and their incorporation into cell production is discussed. Future research and technology trends leading to further efficiency increases and substantial cost reductions are described.
Brandhorst, H. W., Jr.
Plastic Schottky barrier solar cells
A photovoltaic cell structure is fabricated from an active medium including an undoped, intrinsically p-type organic semiconductor comprising polyacetylene. When a film of such material is in rectifying contact with a magnesium electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates the magnesium layer on the undoped polyacetylene film.
Waldrop, James R. (Thousand Oaks, CA); Cohen, Marshall J. (Thousand Oaks, CA)
Concepts of inorganic solid-state nanostructured solar cells
The development of inorganic solid-state nanostructured solar cells over the last years has been reviewed with respect to concepts and materials. Major attention has been paid to solar cells with extremely thin absorber, solar cells with ultra-thin nano-composite absorber and solar cells with quantum dot absorber layers. The focus has been set to structured transparent electron conductors and absorber materials
Thomas Dittrich; Abdelhak Belaidi; Ahmed Ennaoui
NASA Technical Reports Server (NTRS)
The Solar Activity Measurements Experiments (SAMEX) mission is described. It is designed to provide a look at the interactions of magnetic fields and plasmas that create flares and other explosive events on the sun in an effort to understand solar activity and the nature of the solar magnetic field. The need for this mission, the instruments to be used, and the expected benefits of SAMEX are discussed.
Multijunction Solar Cells on Epitaxial Templates
NASA Astrophysics Data System (ADS)
Future ultrahigh efficiency multijunction solar cells will employ designs that feature three or four or more subcells utilizing lattice-mismatched structures to achieve an optimal band gap sequence for solar energy conversion. While lattice-mismatched multijunction cells have been fabricated recently using metamorphic growth approaches, use of direct wafer bonding techniques to enable lattice mismatch accommodation at the subcell interfaces allows considerably more design freedom and inherently higher-quality, defect-free active regions. This thesis presents new results on wafer bonding and layer transfer for integration of materials with large lattice mismatch, as well as modeling work to better understand the key material parameters in the design of new multijunction solar cells. GaInP/GaAs dual junction solar cells on Ge/Si templates were fabricated using wafer bonding and ion implantation induced layer transfer techniques. Following layer transfer, the surface of the �1.4 mum thick transferred Ge(100) has an as-transferred RMS roughness of �20 nm and a near surface layer containing a high density of ion implantation-induced defects. The RMS roughness has been reduced to <1 nm. In addition, the effects of changing the strain state of the template substrate on the performance of the devices has been explored by comparing devices grown on Ge/Si and Ge/sapphire. The CTE mismatch between Si and GaAs/GaInP materials induces a tensile strain, whereas the sapphire substrate induces a compressive strain. An analytical p-n junction device physics model for GaInP/GaAs/InGaAsP/InGaAs four junction solar cells was developed. Real behavior of solar cells is accounted for by including: free carrier absorption, temperature and doping effects on carrier mobility, as well as two recombination pathways: Shockley-Read-Hall recombination from a single mid gap trap level and surface recombination. Upper bounds set by detailed balance calculations can be approached by letting the parameters approach ideal conditions. Detailed balance calculations always benefit from added subcells, current matching requirements in series connected p-n multijunctions indicate a minimum performance required from added subcells for net contribution to the overall device. This model allows novel solar cell structures to be evaluated by providing realistic predictions of the performance limitations of these multijunction devices.
Archer, Melissa Jane
New Materials for Chalcogenide Based Solar Cells
NASA Astrophysics Data System (ADS)
Thin film solar cells based on copper indium gallium diselenide (CIGS) have achieved efficiencies exceeding 20 %. The p-n junction in these solar cells is formed between a p-type CIGS absorber layer and a composite n-type film that consists of a 50-100 nm thin n-type CdS followed by a 50-200 nm thin n-type ZnO. This dissertation focuses on developing materials for replacing CdS and ZnO films to improve the damp-heat stability of the solar cells and for minimizing the use of Cd. Specifically, I demonstrate a new CIGS solar cell with better damp heat stability wherein the ZnO layer is replaced with SnO2. The efficiency of solar cells made with SnO2 decreased less than 5 % after 120 hours at 85 �C and 85 % relative humidity while the efficiency of solar cells made with ZnO declined by more than 70 %. Moreover, I showed that a SnO2 film deposited on top of completed CIGS solar cells significantly increased the device lifetime by forming a barrier against water diffusion. Semicrystalline SnO2 films deposited at room temperature had nanocrystals embedded in an amorphous matrix, which resulted in films without grain boundaries. These films exhibited better damp-heat stability than ZnO and crystalline SnO2 films deposited at higher temperature and this difference is attributed to the lack of grain boundary water diffusion. In addition, I studied CBD of Zn1-xCdxS from aqueous solutions of thiourea, ethylenediaminetetraacetic acid and zinc and cadmium sulfate. I demonstrated that films with varying composition (x) can be deposited through CBD and studied the structure and composition variation along the films' thickness. However, this traditional chemical bath deposition (CBD) approach heats the entire solution and wastes most of the chemicals by homogenous particle formation. To overcome this problem, I designed and developed a continuous-flow CBD approach to utilize the chemicals efficiently and to eliminate homogenous particle formation. Only the substrate is heated to the deposition temperature while the CBD solution is rapidly circulated between the bath and a chilled reservoir. We have demonstrated Zn1-x CdxS films for a variety of (x) values, with and without varying (x) across film thickness.
Tosun, Banu Selin
Optimum operating conditions of a solar cell panel and prediction of solar radiation in Sanaa, Yemen
Results of a study of the performance of solar cells under nominal operating conditions in Yemen are reported. The solar cell panel comprised 14 Si cells of .003 sq m surface area each, and was mounted on a rooftop with the solar radiation being measured by a pyranometer. Further monitoring was performed of the panel surface temperature, the ambient air
A. Khogali; M. R. I. Ramadan
High efficiency crystalline silicon solar cells
NASA Technical Reports Server (NTRS)
A review of the entire research program since its inception ten years ago is given. The initial effort focused on the effects of impurities on the efficiency of silicon solar cells to provide figures of maximum allowable impurity density for efficiencies up to about 16 to 17%. Highly accurate experimental techniques were extended to characterize the recombination properties of the residual imputities in the silicon solar cell. A numerical simulator of the solar cell was also developed, using the Circuit Technique for Semiconductor Analysis. Recent effort focused on the delineation of the material and device parameters which limited the silicon efficiency to below 20% and on an investigation of cell designs to break the 20% barrier. Designs of the cell device structure and geometry can further reduce recombination losses as well as the sensitivity and criticalness of the fabrication technology required to exceed 20%. Further research is needed on the fundamental characterization of the carrier recombination properties at the chemical impurity and physical defect centers. It is shown that only single crystalline silicon cell technology can be successful in attaining efficiencies greater than 20%.
Sah, C. Tang
ISEE-C Solar Wind Plasma Experiment
Two 135� spherical section electrostatic analyzers furnish electron and ion measurements of the solar wind on ISEE-C. Each of these instruments utilizes a divided secondary emitter system to intercept the analyzed particles. Secondary electrons selected from all of the emitters simultaneously provide fast two-dimensional measurements of the particle fluxes integrated over polar angle; at a slower rate secondary electrons are
S. J. Bame; J. R. Asbridge; H. E. Felthauser; J. P. Glore; H. L. Hawk; J. Chavez
Determination of the solar cell panel installation angle
The output power of the solar cell panel is highly affected by the sunlight incident angle. The efficiency can be improved if the solar cell panel is properly installed with the optimum angle. The relationship between the sunlight incident angle and the sunlight radiation intensity on the solar cell panel surface is presented in this paper. Genetic algorithms with climatic
Yaow-Ming Chen; Hsu-Chin Wu
Flexible Solar Cell Arrays for Increased Space Power
The importance of solar cells for space power supplies continues with increased emphasis. The need for advances in the design of solar cell arrays becomes more pressing as the requirement for increased power levels is apparent. This paper discusses a flexible solar cell concept, includes a brief history of the development, describes a conceptual design for a 20-kW array, giving
Kenneth A. Ray
The cooling technology of solar cells under concentrated system
Temperature control is very important to keep the efficiency of solar cells, because the open-circuit voltage of the system is obviously dropped, when the temperature is raised, so as to a decline in output power of solar cells. Especially in the concentrated system, solar cells worked several times even hundreds of times in the irradiation conditions, so the temperature will
Ye Zhangbo; Li Qifen; Zhu Qunzhi; Pan Weiguo
Latest results on semitransparent POWER silicon solar cells
The paper presents the latest results of the polycrystalline wafer engineering result (POWER) silicon solar cell research (G. Willeke, P. Fath, The POWER silicon solar cell, Proceedings of the 12th EPVSEC, Amsterdam, 1994, pp. 766�768). Mono � as well as bifacially active semitransparent silicon solar cells have been created by forming perpendicularly overlapping grooves on the front and the rear
Arnd Boueke; Ralph K�hn; Peter Fath; Gerhard Willeke; Ernst Bucher
Space solar cell technology development - A perspective
NASA Technical Reports Server (NTRS)
The developmental history of photovoltaics is examined as a basis for predicting further advances to the year 2000. Transistor technology was the precursor of solar cell development. Terrestrial cells were modified for space through changes in geometry and size, as well as the use of Ag-Ti contacts and manufacture of a p-type base. The violet cell was produced for Comsat, and involved shallow junctions, new contacts, and an enhanced antireflection coating for better radiation tolerance. The driving force was the desire by private companies to reduce cost and weight for commercial satellite power supplies. Liquid phase epitaxial (LPE) GaAs cells are the latest advancement, having a 4 sq cm area and increased efficiency. GaAs cells are expected to be flight ready in the 1980s. Testing is still necessary to verify production techniques and the resistance to electron and photon damage. Research will continue in CVD cell technology, new panel technology, and ultrathin Si cells.
Scott-Monck, J.
In this talk, I review, from the phenomenological point of view, solutions to the solar neutrino problem, which are not provided by the conventional neutrino oscillation induced by mass and flavor mixing, and show that they can provide a good fit to the observed data. I also consider some simple implications for low energy solar neutrino experiments.
H. Nunokawa
Piezoresistance and solar cell efficiency
NASA Technical Reports Server (NTRS)
Diffusion-induced stresses in silicon are shown to result in large localized changes in the minority-carrier mobility which in turn can have a significant effect on cell output. Evidence is given that both compressive and tensile stresses can be generated in either the emitter or the base region. Tensile stresses in the base appear to be much more effective in altering cell performance than do compressive stresses. While most stress-related effects appear to degrade cell efficiency, this is not always the case. Evidence is presented showing that arsenic-induced stresses can result in emitter characteristics comparable to those found in the MINP cell without requiring a high degree of surface passivation.
Weizer, Victor G.
NASA Astrophysics Data System (ADS)
Increasing energy demand and the parallel increase of greenhouse gas emissions are challenging researchers to find new and cleaner energy sources. Solar energy harvesting is arguably the most promising candidate for replacing fossil-fuel power generation. Photovoltaics are the most direct way of collecting solar energy; cost continues to hinder large-scale implementation of photovoltaics, however. Therefore, alternative technologies that will allow the extraction of solar power, while maintaining the overall costs of fabrication, installation, collection, and distribution low, must be explored. This thesis focuses on the fabrication and testing of two types of devices that step up to this challenge: the luminescent solar concentrator (LSC) and all-inorganic nanoparticle solar cells. In these devices I make use of novel materials, semiconducting polymers and inorganic nanoparticles, both of which have lower costs than the crystalline materials used in the fabrication of traditional photovoltaics. Furthermore, the cost of manufacturing LSCs and the nanoparticle solar cells is lower than the manufacturing cost of traditional optics-based concentrators and crystalline solar cells. An LSC is essentially a slab of luminescent material that acts as a planar light pipe. The LSC absorbs incoming photons and channels fluoresced photons toward appropriately located solar cells, which perform the photovoltaic conversion. By covering large areas with relatively inexpensive fluorescing organic dyes or semiconducting polymers, the area of solar cell needed is greatly reduced. Because semiconducting polymers and quantum dots may have small absorption/emission band overlaps, tunable absorption, and longer lifetimes, they are good candidates for LSC fabrication, promising improvement with respect to laser dyes traditionally used to fabricate LSCs. Here the efficiency of LSCs consisting of liquid solutions of semiconducting polymers encased in glass was measured and compared to the efficiency of LSCs based on small molecule laser dyes and on quantum dots. Factors affecting the optical efficiency of the system such as the luminescing properties of the fluorophors were examined. The experimental results were compared to Monte-Carlo simulations. Our results suggest that commercially available quantum dots cannot serve as viable LSC dyes because of large absorption/emission band overlap and relatively low quantum yield. Materials such as Red F demonstrate that semi-conducting polymers with high quantum yield and small absorption/emission band overlap are good candidates for LSCs. Recently, a solar cell system based purely on CdSe and Cite nanoparticles as the absorbing materials was proposed ans it was suggested that its operational mechanism was that of polymer donor/acceptor systems. Here we present solar cells consisting of a sintered active bilayer of CdSe and PbSe nanoparticles in the structure ITO/CdSe/interlayer/PbSe/Al, where an interlayer of LiF or Al2O3 was found necessary to prevent low shunt resistance from suppressing the photovoltaic behavior. We fabricated unoptimized solar cells with a short-circuit current of 6 mA/cm2, an open-circuit voltage of 0.18 V, and a fill factor of 41%. External quantum efficiency spectra revealed that photons from the infrared portion of the spectrum were not collected, suggesting that the low bandgap PbSe film did not contribute to the photocurrent of the structure despite exhibiting photoconductivity. Other measurements, however, showed that the PbSe film was indeed necessary to produce a photovoltage and transport electrons. Through sintering, the nanoparticle films acquired bandgaps similar to those of the corresponding bulk materials and became more conductive. Because the PbSe films were found to be considerably more conductive than the CdSe ones, we suggest that the PbSe layer is effectively behaving like a low conductivity electrical contact. Therefore, in contrast to the photovoltaics presented in the seminal research on CdSe/Cite solar cells, the CdSe/PbSe solar cell system presented here d
Sholin, Veronica
NASA Astrophysics Data System (ADS)
An initial study using electron beam induced current (EBIC) to evaluate solar cells has been carried out with the large chamber scanning electron microscope (LC-SEM) at the Western Kentucky University Nondestructive Analysis Center. EBIC is a scanning electron microscope technique used for the characterization of semiconductors. To facilitate our studies, we developed a Solar Amplification System (SASY) for analyzing current distribution and defects within a solar cell module. Preliminary qualitative results will be shown for a solar cell module that demonstrates the viability of the technique using the LC-SEM. Quantitative EBIC experiments will be carried out to analyze defects and minority carrier properties. Additionally, a well-focused spot of light from an LED mounted at the side of the SEM column will scan the same area of the solar cell using the LC-SEM positioning system. SASY will then output the solar efficiency to be compared with the minority carrier properties found using EBIC.
Wink, Tara; Kintzel, Edward; Marienhoff, Peter; Klein, Martin
Hypervelocity Impact Studies on Solar Cell Modules
NASA Technical Reports Server (NTRS)
Space environmental effects have caused severe problems as satellites move toward increased power and operating voltage levels. The greatest unknown, however, is the effect of high velocity micrometeoroid impacts on high voltage arrays (>200V). Understanding such impact phenomena is necessary for the design of future reliable, high voltage solar arrays, especially for Space Solar Power applications. Therefore, the objective of this work was to study the effect of hypervelocity impacts on high voltage solar arrays. Initially, state of the art, 18% efficient GaAs solar cell strings were targeted. The maximum bias voltage on a two-cell string was -200 V while the adjacent string was held at -140 V relative to the plasma potential. A hollow cathode device provided the plasma. Soda lime glass particles 40-120 micrometers in diameter were accelerated in the Hypervelocity Impact Facility to velocities as high as 11.6 km/sec. Coordinates and velocity were obtained for each of the approximately 40 particle impact sites on each shot. Arcing did occur, and both discharging and recharging of arcs between the two strings was observed. The recharging phenomena appeared to stop at approximately 66V string differential. No arcing was observed at 400 V on concentrator cell modules for the Stretched Lens Array.
Brandhorst, Henry W., Jr.; Best, Stevie R.
Enhancing Solar Cell Efficiencies through 1-D Nanostructures
The current global energy problem can be attributed to insufficient fossil fuel supplies and excessive greenhouse gas emissions resulting from increasing fossil fuel consumption. The huge demand for clean energy potentially can be met by solar-to-electricity conversions. The large-scale use of solar energy is not occurring due to the high cost and inadequate efficiencies of existing solar cells. Nanostructured materials have offered new opportunities to design more efficient solar cells, particularly one-dimensional (1-D) nanomaterials for enhancing solar cell efficiencies. These 1-D nanostructures, including nanotubes, nanowires, and nanorods, offer significant opportunities to improve efficiencies of solar cells by facilitating photon absorption, electron transport, and electron collection; however, tremendous challenges must be conquered before the large-scale commercialization of such cells. This review specifically focuses on the use of 1-D nanostructures for enhancing solar cell efficiencies. Other nanostructured solar cells or solar cells based on bulk materials are not covered in this review. Major topics addressed include dye-sensitized solar cells, quantum-dot-sensitized solar cells, and p-n junction solar cells.
The emergence of perovskite solar cells
NASA Astrophysics Data System (ADS)
The past two years have seen the unprecedentedly rapid emergence of a new class of solar cell based on mixed organic-inorganic halide perovskites. Although the first efficient solid-state perovskite cells were reported only in mid-2012, extremely rapid progress was made during 2013 with energy conversion efficiencies reaching a confirmed 16.2% at the end of the year. This increased to a confirmed efficiency of 17.9% in early 2014, with unconfirmed values as high as 19.3% claimed. Moreover, a broad range of different fabrication approaches and device concepts is represented among the highest performing devices -- this diversity suggests that performance is still far from fully optimized. This Review briefly outlines notable achievements to date, describes the unique attributes of these perovskites leading to their rapid emergence and discusses challenges facing the successful development and commercialization of perovskite solar cells.
Green, Martin A.; Ho-Baillie, Anita; Snaith, Henry J.
Winter experience of a passive solar retrofit
NASA Astrophysics Data System (ADS)
An older home in St. Louis had 2 inch foam insulation added to the outside of masonry walls with stucco exterior finish applied. The south wall was modified so that there is a gross solar collection area of 26.2 square m, with 13.2 square m of greenhouse, 8.6 square m of direct gain and 4.4 square m of Trombe components. The performance of the building and its data acquisition system are described.
Michels, T. I.; Andes, F. S.
Solar Airplanes and Regenerative Fuel Cells
NASA Technical Reports Server (NTRS)
A solar electric aircraft with the potential to "fly forever" has captured NASA's interest, and the concept for such an aircraft was pursued under Aeronautics Environmental Research Aircraft and Sensor Technology (ERAST) project. Feasibility of this aircraft happens to depend on the successful development of solar power technologies critical to NASA's Exploration Initiatives; hence, there was widespread interest throughout NASA to bring these technologies to a flight demonstration. The most critical is an energy storage system to sustain mission power during night periods. For the solar airplane, whose flight capability is already limited by the diffuse nature of solar flux and subject to latitude and time of year constraints, the feasibility of long endurance flight depends on a storage density figure of merit better than 400-600 watt-hr per kilogram. This figure of merit is beyond the capability of present day storage technologies (other than nuclear) but may be achievable in the hydrogen-oxygen regenerative fuel cell (RFC). This potential has led NASA to undertake the practical development of a hydrogen-oxygen regenerative fuel cell, initially as solar energy storage for a high altitude UAV science platform but eventually to serve as the primary power source for NASAs lunar base and other planet surface installations. Potentially the highest storage capacity and lowest weight of any non-nuclear device, a flight-weight RFC aboard a solar-electric aircraft that is flown continuously through several successive day-night cycles will provide the most convincing demonstration that this technology's widespread potential has been realized. In 1998 NASA began development of a closed cycle hydrogen oxygen PEM RFC under the Aeronautics Environmental Research Aircraft and Sensor Technology (ERAST) project and continued its development, originally for a solar electric airplane flight, through FY2005 under the Low Emissions Alternative Power (LEAP) project. Construction of the closed loop system began in 2002 at the NASA Glenn Research Center in Cleveland, Ohio. System checkout was completed, and testing began, in July of 2003. The initial test sequences were done with only a fuel cell or electrolyzer in the test rig. Those tests were used to verify the test apparatus, procedures, and software. The first complete cycles of the fully closed loop, regenerative fuel cell system were successfully completed in the following September. Following some hardware upgrades to increase reactant recirculation flow, the test rig was operated at full power in December 2003 and again in January 2004. In March 2004 a newer generation of fuel cell and electrolyzer stacks was substituted for the original hardware and these stacks were successfully tested at full power under cyclic operation in June of 2004.
Bents, David J.
Deng & Schiff, Amorphous Silicon Based Solar Cells rev. 7/30/2002, Page 1 Amorphous Silicon Based Solar Cells Xunming Deng and Eric A. Schiff Table of Contents 1 Overview 3 1.1 Amorphous Silicon: The First Bipolar Amorphous Semiconductor 3 1.2 Designs for Amorphous Silicon Solar Cells: A Guided Tour 6
Deng, Xunming
Photovoltaic linear concentrator arrays can benefit from high performance solar cell technologies being developed at AstroPower. Specifically, these are the integration of thin GaAs solar cell and epitaxial lateral overgrowth technologies with the application of monolithically interconnected solar cell (MISC) techniques. This MISC array has several advantages which make it ideal for space concentrator systems. These are high system voltage,
L. C. Dinetta; M. H. Hannon
Thermal runaway in multijunction solar cells
NASA Astrophysics Data System (ADS)
A small fraction of GaInP2/GaAs/Ge triple junction solar cells exposed to the 6� concentrated air mass zero spectrum at 523 K for 5 min was found to be severely shunted afterwards. A combination of electroluminescence imaging and focused ion beam cross sectioning revealed that pre-existing top-middle cell shunts were responsible for the observed degradation. Joule heating in the shunt resistance limiting Ge substrate is modeled and exhibits a thermal runaway effect above a critical voltage, in agreement with the experimental observation. The implications for current and future multijunction cells are discussed.
Zimmermann, Claus G.
Advanced high efficiency wraparound contact solar cell
NASA Technical Reports Server (NTRS)
A significant advancement in the development of thin high efficiency wraparound contact silicon solar cells has been made by coupling space and terrestrial processing procedures. Although this new method for fabricating cells has not been completely reduced to practice, some of the initial cells have delivered over 20 mW/sq cm when tested at 25 C under AMO intensity. This approach not only yields high efficiency devices, but shows promise of allowing complete freedom of choice in both the location and size of the wraparound contact pad area.
Scott-Monck, J. A.; Uno, F. M.; Thornhill, J. W.
Multijunction high voltage concentrator solar cells
NASA Technical Reports Server (NTRS)
The standard integrated circuit technology has been developed to design and fabricate new innovative planar multi-junction solar cell chips for concentrated sunlight applications. This 1 cm x 1 cm cell consisted of several voltage generating regions called unit cells which were internally connected in series within a single chip resulting in high open circuit voltages. Typical open-circuit voltages of 3.6 V and short-circuit currents of 90 ma were obtained at 80 AM1 suns. A dramatic increase in both short circuit current and open circuit voltage with increased light levels was observed.
Valco, G. J.; Kapoor, V. J.; Evans, J. C.; Chai, A.-T.
Development of integral covers on solar cells
NASA Technical Reports Server (NTRS)
The electron-beam technique for evaporating a dielectric material onto solar cells is investigated. A process has been developed which will provide a highly transparent, low stress, 2 mil thick cover capable of withstanding conventional space type qualification tests including humidity, thermal shock, and thermal cycling. The covers have demonstrated the ability to withstand 10 to the 15th power 1 MeV electrons and UV irradiation with minor darkening. Investigation of the cell AR coating has produced a space qualifiable titanium oxide coating which will give an additional 6% current output over similar silicon oxide coated cells when covered by glass.
Stella, P.; Somberg, H.
One-sun silicon solar cell research
NASA Astrophysics Data System (ADS)
This report describes research for the period September 1988 to February 1990 directed at improving the performance of crystalline and polycrystalline silicon solar cells. Key results include the demonstration of 24.2 percent energy conversion efficiency for 4-sq cm crystalline cells fabricated using the development of the Passivated Emitter Cell processing sequence, the demonstration of energy conversion efficiency up to 22.4 percent for large-area, low-cost silicon concentrator cells fabricated using the laser grooved cell processing sequence, the demonstration of efficiencies up to 17.8 percent on 4-sq cm polycrystalline silicon substrates, and the demonstration of efficiencies of up to 16.7 percent on 10 sq cm polycrystalline substrates using a combined laser textured and grooved cell processing sequence.
Green, M. A.; Zhao, J.; Wang, A.; Blakers, A. W.; Milne, A. M.; Dai, X.; Chong, C. M.; Wenham, S. R.; Zhang, F.; Yun, F.
Device Physics of Nanoscale Interdigitated Solar Cells (Poster)
Nanoscale interdigitated solar cell device architectures are being investigated for organic and inorganic solar cell devices. Due to the inherent complexity of these device designs quantitative modeling is needed to understand the device physics. Theoretical concepts have been proposed that nanodomains of different phases may form in polycrystalline CIGS solar cells. These theories propose that the nanodomains may form complex 3D intertwined p-n networks that enhance device performance.Recent experimental evidence offers some support for the existence of nanodomains in CIGS thin films. This study utilizes CIGS solar cells to examine general and CIGS-specific concepts in nanoscale interdigitated solar cells.
Metzger, W.; Levi, D.
An outlook for automated CIS solar cell factory
Recent experimental work on single-crystal silicon conductor-insulator-semiconductor (CIS) solar cells indicates that the performance of these devices is close to that of the best p-n junction solar cells. The CIS structure is a candidate in the manufacture of large-scale solar energy conversion arrays. It is noted that the stage is now set for the commercial production of these solar cells.
K. Rajkanan; R. Singh
Characterization of Low Temperature Deposited Flexible Amorphous Silicon Solar Cells
N-i-p structure amorphous silicon solar cells deposited on flexible and glass substrates are successfully fabricated at low substrate temperature of 100�C through plasma enhanced chemical vapor deposition (PECVD) system. The external parameters of solar cells are characterized by solar simulator. The results indicate the best dot of the solar cells with glass substrate can reach to 5.54% of conversion efficiency
Yingge Li; Dongxing Du
Efficient Cells Cut the Cost of Solar Power
NASA Technical Reports Server (NTRS)
If you visit Glenn Research Center, you might encounter a photovoltaic (PV) array that looks unlike anything you've ever seen. In fact, what one would normally identify as the panel is actually a series of curved mirrors called solar concentrators, engineered to reflect sunlight rather than absorb it. These concentrators gather, intensify, and focus sun beams upward, aiming at a fixture containing specialized silicon concentrated PV chips the actual solar cells. If you stay by the array for a while, you'll notice that the solar concentrators follow the path of the sun throughout the day, changing position to best capture and utilize the sunlight. The specialized chips that make the technology possible are the brainchild of Bernard Sater, an engineer who had worked at Glenn since the early 1960s before retiring to pursue his unique ideas for harnessing solar power. Sater contributed to multiple PV projects in the latter part of his career at the Center, including research and development on the International Space Station s solar arrays. In his spare time, he enjoyed tinkering with new approaches to solar power, experiments that resulted in the system installed at Glenn today. Sater s basic idea had two components. First, he wanted to create a silicon cell that was smaller, more efficient, and much lower cost than those available at the time. To ensure that the potential of such a chip could be realized, he also planned on pairing it with a system that could concentrate sunlight and focus it directly on the cell. When he retired from Glenn in 1994 to focus on researching and developing the technology full time, Sater found that NASA was interested in the concept and ready to provide funding, facilities, and expertise in order to assist in its development.
Semi-transparent inverted organic solar cells
NASA Astrophysics Data System (ADS)
We will present efficient semi-transparent bulk-heterojunction [regioregular of poly(3-hexylthiophene): (6,6)-phenyl C61 butyric acid methyl ester] solar cells with an inverted device architecture. Highly transparent ZnO and TiO2 films prepared by Atomic Layer Deposition are used as cathode interlayers on top of ITO. The topanode consists of a RF-sputtered ITO layer. To avoid damage due to the plasma deposition of this layer, a sputtering buffer layer of MoO3 is used as protection. This concept allows for devices with a transmissivity higher than 60 % for wavelengths 650 nm. The thickness of the MoO3 buffer has been varied in order to study its effect on the electrical properties of the solar cell and its ability to prevent possible damage to the organic active layers upon ITO deposition. Without this buffer or for thin buffers it has been found that device performance is very poor concerning the leakage current, the fill factor, the short circuit current and the power conversion efficiencies. As a reference inverted solar cells with a metal electrode (Al) instead of the ITO-top contact are used. The variation between the PCE of top versus conventional illumination of the semi-transparent cells was also examined and will be interpreted in view of the results of the optical simulation of the dielectric device stack with and without reflection top electrode. Power conversion efficiencies of 2-3 % for the opaque inverted solar cells and 1.5-2.5 % for the semi-transparent devices were obtained under an AM1.5G illumination.
Schmidt, H.; Winkler, T.; Tilgner, M.; Fl�gge, H.; Schmale, S.; B�low, T.; Meyer, J.; Johannes, H.-H.; Riedl, T.; Kowalsky, W.
Silicon solar cell process development, fabrication, and analysis
NASA Technical Reports Server (NTRS)
Solar cells from HEM, Dendritic Webs, and EFG ribbons were fabricated and characterized. The HEM solar cells showed only slight enhancement in cell performance after gettering steps (diffusion glass) were added. Dendritic webs from various growth runs indicated that performance of solar cells made from the webs was not as good as that of the conventional CZ cells. The EFG ribbons grown in CO ambient showed significant improvement in silicon quality.
Yoo, H. I.; Iles, P. A.; Leung, D. C.
The Baksan gallium solar neutrino experiment
A radiochemical /sup 71/Ga-/sup 71/Ge experiment to determine the integral flux of neutrinos from the sun has been constructed at the Baksan Neutrino Observatory in the USSR. Measurements have begun with 30 tonnes of gallium. The experiment is being expanded with the addition of another 30 tonnes. The motivation, experimental procedures, and present status of this experiment are presented. 43 refs., 1 fig., 1 tab.
Gavrin, V.N.; Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.L.; Bychuk, O.V.; Danshin, S.N.; Eroshkina, L.A.; Faizov, E.L.; Gayevsky, V.I.; Girin, S.V.
Recent advances in sensitized mesoscopic solar cells.
Perhaps the largest challenge for our global society is to find ways to replace the slowly but inevitably vanishing fossil fuel supplies by renewable resources and, at the same time, avoid negative effects from the current energy system on climate, environment, and health. The quality of human life to a large degree depends upon the availability of clean energy sources. The worldwide power consumption is expected to double in the next 3 decades because of the increase in world population and the rising demand of energy in the developing countries. This implies enhanced depletion of fossil fuel reserves, leading to further aggravation of the environmental pollution. As a consequence of dwindling resources, a huge power supply gap of 14 terawatts is expected to open up by year 2050 equaling today's entire consumption, thus threatening to create a planetary emergency of gigantic dimensions. Solar energy is expected to play a crucial role as a future energy source. The sun provides about 120,000 terawatts to the earth's surface, which amounts to 6000 times the present rate of the world's energy consumption. However, capturing solar energy and converting it to electricity or chemical fuels, such as hydrogen, at low cost and using abundantly available raw materials remains a huge challenge. Chemistry is expected to make pivotal contributions to identify environmentally friendly solutions to this energy problem. One area of great promise is that of solar converters generally referred to as "organic photovoltaic cells" (OPV) that employ organic constituents for light harvesting or charge carrier transport. While this field is still in its infancy, it is receiving enormous research attention, with the number of publications growing exponentially over the past decade. The advantage of this new generation of solar cells is that they can be produced at low cost, i.e., potentially less than 1 U.S. $/peak watt. Some but not all OPV embodiments can avoid the expensive and energy-intensive high vacuum and materials purification steps that are currently employed in the fabrication of all other thin-film solar cells. Organic materials are abundantly available, so that the technology can be scaled up to the terawatt scale without running into feedstock supply problems. This gives organic-based solar cells an advantage over the two major competing thin-film photovoltaic devices, i.e., CdTe and CuIn(As)Se, which use highly toxic materials of low natural abundance. However, a drawback of the current embodiment of OPV cells is that their efficiency is significantly lower than that for single and multicrystalline silicon as well as CdTe and CuIn(As)Se cells. Also, polymer-based OPV cells are very sensitive to water and oxygen and, hence, need to be carefully sealed to avoid rapid degradation. The research discussed within the framework of this Account aims at identifying and providing solutions to the efficiency problems that the OPV field is still facing. The discussion focuses on mesoscopic solar cells, in particular, dye-sensitized solar cells (DSCs), which have been developed in our laboratory and remain the focus of our investigations. The efficiency problem is being tackled using molecular science and nanotechnology. The sensitizer constitutes the heart of the DSC, using sunlight to pump electrons from a lower to a higher energy level, generating in this fashion an electric potential difference, which can exploited to produce electric work. Currently, there is a quest for sensitizers that achieve effective harnessing of the red and near-IR part of sunlight, converting these photons to electricity better than the currently used generation of dyes. Progress in this area has been significant over the past few years, resulting in a boost in the conversion efficiency of the DSC that will be reviewed. PMID:19715294
Gr�tzel, Michael
Linking solar and long baseline terrestrial neutrino experiments
We show that in the framework of three light neutrino species with hierarchical masses and assuming no fine tuning between the entries of the neutrino mass matrix, one can use the solar neutrino data to obtain information on the element $U_{e3}$ of the lepton mixing matrix. Conversely, a measurement of $U_{e3}$ in atmospheric or long baseline accelerator or reactor neutrino experiments would help discriminate between possible oscillation solutions of the solar neutrino problem.
E. Kh. Akhmedov; G. C. Branco; M. N. Rebelo
NASA Technical Reports Server (NTRS)
The CTS solar array technology experiment which consists of a solar cell test patch on the Kapton-substrate solar array and the appertaining electronics unit has been operating in geostationary orbit for nearly 1 year without any malfunction although it is expected to be strongly influenced by charging effects on the array surface. The results of a post-launch test program show that the experiment would not survive a discharge due to electrostatic charging in the test patch area. In a simulated substorm, environment discharges were obtained only below a temperature threshold of about 30 C. With solar illumination, this threshold is reduced below 0 C.
Bogus, K. P.
NASA Astrophysics Data System (ADS)
We introduce a p-i-n-type heterojunction architecture for organic solar cells where the active region is sandwiched between two doped wide-gap layers. The term p-i-n means here a layer sequence in the form p-doped layer, intrinsic layer and n-doped layer. The doping is realized by controlled co-evaporation using organic dopants and leads to conductivities of 10-4 to 10-5 S/cm in the p- and n-doped wide-gap layers, respectively. The photoactive layer is formed by a mixture of phthalocyanine zinc (ZnPc) and the fullerene C60 and shows mainly amorphous morphology. As a first step towards p-i-n structures, we show the advantage of using wide-gap layers in M-i-p-type diodes (metal layer-intrinsic layer-p-doped layer). The solar cells exhibit a maximum external quantum efficiency of 40% between 630-nm and 700-nm wavelength. With the help of an optical multilayer model, we optimize the optical properties of the solar cells by placing the active region at the maximum of the optical field distribution. The results of the model are largely confirmed by the experimental findings. For an optically optimized device, we find an internal quantum efficiency of around 82% under short-circuit conditions. Adding a layer of 10-nm thickness of the red material N,N'-dimethylperylene-3,4:9,10-dicarboximide (Me-PTCDI) to the active region, a power-conversion efficiency of 1.9% for a single cell is obtained. Such optically thin cells with high internal quantum efficiency are an important step towards high-efficiency tandem cells. First tandem cells which are not yet optimized already show 2.4% power-conversion efficiency under simulated AM 1.5 illumination of 125 mW/cm2 .
Maennig, B.; Drechsel, J.; Gebeyehu, D.; Simon, P.; Kozlowski, F.; Werner, A.; Li, F.; Grundmann, S.; Sonntag, S.; Koch, M.; Leo, K.; Pfeiffer, M.; Hoppe, H.; Meissner, D.; Sariciftci, N. S.; Riedel, I.; Dyakonov, V.; Parisi, J.
Outgassing of Flown and Unflown MIR Solar Cells
NASA Technical Reports Server (NTRS)
A solar panel array with more than ten years space exposure was removed from the Mir core module in November 1997, and an eight panel section was returned to Earth in January 1998. Several solar cells were removed from panel eight of the returned array and placed in a high vacuum system with a residual gas analyzer (200 amu mass spectrometer) and a cold finger. Similar unflown solar cells of the same vintage were later obtained from Energia. Several of the unflown cells were also placed in the vacuum system and outgassed residues were collected on the LN2 cold finger. Almost 3 mg of outgassed residue was collected -from a string of three unflown solar cells over a period of 94 hours under vacuum. The collected residue was weighed with a microbalance, and then the residue was analyzed by FTIR spectroscopy, and by gas chromatograph-mass spectroscopy. About 25 outgassed constituents were separated by the gas chromatograph, and a high-resolution mass spectrum was obtained of each constituent. Molecular identifications have been made for the constituents. The constituents are primarily cyclic siloxanes, and several of the constituents are isomers of the same molecule. Most of the outgassed constituents have a molecular mass of about 500 amu. Almost one mg of residue was extracted from one sq cm of coverglass/adhesive from a flown solar cell by soaking in isopropyl alcohol for 30 minutes. The gas chromatograph separated about 20 constituents. The constituents are mostly cyclic siloxanes with linear branches, hydrocarbons, and phthalates. The typical molecular mass is about 600 amu. These identifications of specific outgassing molecules have resulted in a more complete understanding of the SiO(x) contamination on the Mir solar cell coverglasses, and on the MEEP experiment trays and optical specimens during the Shuttle-Mir Phase One flight experiment program. Adjusted outgassing rates based on the data reported here, and/or measured outgassing rates and specific molecular identifications of ISS hardware samples are needed to input into model predictions of induced environment effects of the ISS.
Harvey, Gale A.; Kinard, William H.; Wilson, Linda A.
Gallium arsenide solar cell radiation damage study
NASA Technical Reports Server (NTRS)
A thorough analysis has been made of electron- and proton- damaged GaAs solar cells suitable for use in space. It is found that, although some electrical parametric data and spectral response data are quite similar, the type of damage due to the two types of radiation is different. An I-V analysis model shows that electrons damage the bulk of the cell and its currents relatively more, while protons damage the junction of the cell and its voltages more. It is suggested that multiple defects due to protons in a strong field region such as a p/n junction cause the greater degradation in cell voltage, whereas the individual point defects in the quasi-neutral minority-carrier-diffusion regions due to electrons cause the greater degradation in cell current and spectral response.
Maurer, R. H.; Herbert, G. A.; Kinnison, J. D.; Meulenberg, A.
Accelerated stress testing of terrestrial solar cells
NASA Technical Reports Server (NTRS)
The development of an accelerated test schedule for terrestrial solar cells is described. This schedule, based on anticipated failure modes deduced from a consideration of IC failure mechanisms, involves bias-temperature testing, humidity testing (including both 85-85 and pressure cooker stress), and thermal-cycle thermal-shock testing. Results are described for 12 different unencapsulated cell types. Both gradual electrical degradation and sudden catastrophic mechanical change were observed. These effects can be used to discriminate between cell types and technologies relative to their reliability attributes. Consideration is given to identifying laboratory failure modes which might lead to severe degradation in the field through second quadrant operation. Test results indicate that the ability of most cell types to withstand accelerated stress testing depends more on the manufacturer's design, processing, and worksmanship than on the particular metallization system. Preliminary tests comparing accelerated test results on encapsulated and unencapsulated cells are described.
Lathrop, J. W.; Hawkins, D. C.; Prince, J. L.; Walker, H. A.
Thin-film polycrystalline silicon solar cells
NASA Astrophysics Data System (ADS)
Thirty-four new solar cells were fabricated on Wacker Sislo substrates and the AM-1 parameters were measured. A detailed comparison was made between the measurement of minority carrier diffusion length by the OE method and the penetrating light laser scan grain boundary photoresponse linewidth method. The laser scan method has more experimental uncertainty and agrees within 10 to 50% with the QE method. It allows determination of L over a large area. Atomic hydrogen passivation studies continued on Wacker material by three techniques. A method of determining surface recombination velocity, s, from laser scan data was developed. No change in s in completed solar cells after H-plasma treatment was observed within experimental error. H-passivation of bare silicon cars as measured by the new laser scan photoconductivity technique showed very large effects.
Funghnan, B. W.; Blanc, J.; Phillips, W.; Redfield, D.
Imprinting localized plasmons for enhanced solar cells.
Imprinted silver nanovoid arrays are investigated via angle-resolved reflectometry to demonstrate their suitability for plasmonic light trapping. Both wavelength- and subwavelength-scale nanovoids are imprinted into standard solar cell architectures to achieve nanostructured metallic electrodes which provide enhanced absorption for improving solar cell performance. The technique is versatile, low-cost and scalable and can be applied to a wide range of organic semiconductors. Absorption features which are independent of incident polarization and weakly dependent on incident angle reveal localized plasmonic modes at the structured interface. Metallic nanostructure-PCPDTBT:PCBM samples demonstrate absorption enhancements of up to 40%. The structured interface provides light trapping, which boosts absorption at wavelengths where the semiconductors absorb poorly. PMID:22948008
Dunbar, Ricky B; Pfadler, Thomas; Lal, Niraj N; Baumberg, Jeremy J; Schmidt-Mende, Lukas
Development of GaAs solar cells
NASA Technical Reports Server (NTRS)
Solar cells and mesa diodes were fabricated by the implantation of zinc or beryllium ions into n-type gallium arsenide. Annealing temperatures above 750 C (zinc) or 650 C (beryllium) were found to produce 50% to 100% activation of the implanted ions. Junction depths of about 0.4 micron were produced by 600 keV zinc implants or 70 keV beryllium implants. P-layer sheet resistance was about 150 ohms for 2 x 10 to the 15th power cm/2 zinc or 1 x 10 to the 15th power cm/2 beryllium implants. This is sufficiently low for efficient solar cell fabrication. Contacting procedures were improved to yield reproducibly adherent, low resistance front and back contacts.
Atomic Layer Deposition of zinc oxide for solar cell applications
NASA Astrophysics Data System (ADS)
Atomic Layer Deposition (ALD) is a vapor phase thin film deposition technique, performed at low substrate temperatures, which enables the deposition of extremely uniform thin films. This technique is scalable up to very large substrates, making it very interesting for industrial applications. On the other hand, ZnO, both undoped and aluminum doped is commonly used as a transparent electrode in solar cells based on Cu(In,Ga)Se2 (CIGS), and is usually deposited by Physical Vapor Deposition techniques. In this paper, we investigate the potential of ALD for the deposition of ZnO windows for solar cell applications. Thin films of a few hundreds of nanometers were grown by ALD, both undoped and doped with aluminum. They were studied by X-ray diffraction, electrical transport measurements, Atomic Force Microscopy and transmittance experiments.
Moret, M.; Abou Chaaya, A.; Bechelany, M.; Miele, P.; Robin, Y.; Briot, O.
Spin dependent photocurrents in ribbon solar cells
Spin Dependent Transport (SDT) is a method of identifying recombination centers which employs a microwave resonance condition to affect the recombination rate of minority carriers in a device. When this technique is used to analyze the diffusion-limited currents produced by long-wavelength optical excitation, it has the potential to chemically identify the major recombination sites in solar cells. We have used this resonance technique to analyze short circuit photocurrents in Edge-defined film-Fed Growth (EFG) ribbon silicon solar cells. At room temperature, our observed photocurrent resonances have zero-crossing g values and linewidths which are similar to SDT observations made on the trans-barrier currents in silicon bicrystals, and electron spin resonance signals seen in damaged silicon, and polycrystalline silicon. These dangling-bond-like SDT signals depend on cell illumination levels in a way that suggests that the values of recombination velocity at electrically active linear boundaries decrease with illumination intensity. Hydrogen processed cells show markedly smaller SDT response, consistent with the passivation of Si dangling bond defects. While most of our SDT observations have been made on n{sup +}/p EFG cells, we suggest that measurements made at low temperatures on other cell structures might uncover resonances due to other recombination centers in this material.
Seager, C.H.; Venturini, E.L.; Schubert, W.K.
New high-efficiency silicon solar cells
NASA Technical Reports Server (NTRS)
A design for silicon solar cells was investigated as an approach to increasing the cell open-circuit voltage and efficiency for flat-plate terrestrial photovoltaic applications. This deviates from past designs, where either the entire front surface of the cell is covered by a planar junction or the surface is textured before junction formation, which results in an even greater (up to 70%) junction area. The heavily doped front region and the junction space charge region are potential areas of high recombination for generated and injected minority carriers. The design presented reduces junction area by spreading equidiameter dot junctions across the surface of the cell, spaced about a diffusion length or less from each other. Various dot diameters and spacings allowed variations in total junction area. A simplified analysis was done to obtain a first-order design optimization. Efficiencies of up to 19% can be obtained. Cell fabrication involved extra masking steps for selective junction diffusion, and made surface passivation a key element in obtaining good collection. It also involved photolithography, with line widths down to microns. A method is demonstrated for achieving potentially high open-circuit voltages and solar-cell efficiencies.
Daud, T.; Crotty, G. T.
Variation of solar cell sensitivity and solar radiation on tilted surfaces
NASA Technical Reports Server (NTRS)
The validity is studied that one of various insolation models used to compute solar radiation incident on tilted surfaces from global data measured on horizontal surfaces. The variation of solar cell sensitivity to solar radiation is determined over a wide range of atmospheric condition. A new model was formulated that reduced the deviations between measured and predicted insolation to less than 3 percent. Evaluation of solar cell sensitivity data indicates small change (2-3 percent) in sensitivity from winter to summer for tilted cells. The feasibility of using such global data as a means for calibrating terrestrial solar cells is discussed.
Klucher, T. M.
Next generation CIGS for solar cells
An overview is presented of the PV-ACIST project. The goal of this project is to demonstrate proof-of-concept of next generation CuIn1-xGax(SySe1-y)2 (CIGS)-based solar cells. The first phase of the project began with a theoretical analysis of the potential of tandem-junction devices. This analysis showed that efficiencies could exceed 25% based constituent junctions comparable to the best achieved in single CIGS
A. Rockett; R. Birkmire; D. Morel; S. Fonash; J.-Y. Hou; M. Marudachalam; J. D'Amico; P. Panse; S. Zafar; D. J. Schroeder
Dip-Coating Fabrication of Solar Cells
NASA Technical Reports Server (NTRS)
Inexpensive silicon solar cells made by simple dip technique. Cooling shoes direct flow of helium on graphite-coated ceramic substrate to solidify film of liquid silicon on graphite surface as substrate is withdrawn from molten silicon. After heaters control cooling of film and substrate to prevent cracking. Gas jets exit at points about 10 mm from substrate surfaces and 6 to 10 mm above melt surface.
Koepke, B.; Suave, D.
Solar-hydrogen fuel-cell vehicles
Hydrogen is an especially attractive transportation fuel. It is the least populating fuel available, and can be produced anywhere there is water and a clean source of electricity. A fuel cycle in which hydrogen is produced by solar-electrolysis of water, or by gasification of renewably grown biomass, and then used in a fuel-cell powered electric-motor vehicle (FCEV), would produce little
Mark A. DeLuchi; Joan M. Ogden
The photophysics of perovskite solar cells
NASA Astrophysics Data System (ADS)
Solution-processed hybrid organic-inorganic perovskite solar cells, a newcomer to the photovoltaic arena, have taken the field by storm with their extraordinary power conversion efficiencies exceeding 17%. In this paper, the photophysics and the latest findings on the carrier dynamics and charge transfer mechanisms in this new class of photovoltaic material will be examined and distilled. Some open photophysics questions will also be discussed.
Sum, Tze Chien
High efficiency silicon solar cell review
NASA Technical Reports Server (NTRS)
An overview is presented of the current research and development efforts to improve the performance of the silicon solar cell. The 24 papers presented reviewed experimental and analytic modeling work which emphasizes the improvment of conversion efficiency and the reduction of manufacturing costs. A summary is given of the round-table discussion, in which the near- and far-term directions of future efficiency improvements were discussed.
Godlewski, M. P. (editor)
Silicon Ink high efficiency solar cells
Innovalight has developed the Cougar� Process, a method for making a high efficiency solar cell on a Cz-Si wafer with a proprietary Silicon Ink. With the use of an industrial inkjet printer, an n-type ink is deposited on a p-type silicon wafer in order to form a high efficiency selective emitter. The Cougar Process requires only an incremental modification to
Homer Antoniadis
Modeling of high efficiency solar cells under laser pulse for power beaming applications
NASA Technical Reports Server (NTRS)
Solar cells have been used to convert sunlight to electrical energy for many years and also offer great potential for non-solar energy conversion applications. Their greatly improved performance under monochromatic light compared to sunlight, makes them suitable as photovoltaic (PV) receivers in laser power beaming applications. Laser beamed power to a PV array receiver could provide power to satellites, an orbital transfer vehicle, or a lunar base. Gallium arsenide (GaAs) and indium phosphide (InP) solar cells have calculated efficiencies of more than 50 percent under continuous illumination at the optimum wavelength. Currently high power free-electron lasers are being developed which operate in pulsed conditions. Understanding cell behavior under a laser pulse is important in the selection of the solar cell material and the laser. An experiment by NAsA lewis and JPL at the AVLIS laser facility in Livermore, CA presented experimental data on cell performance under pulsed laser illumination. Reference 5 contains an overview of technical issues concerning the use of solar cells for laser power conversion, written before the experiments were performed. As the experimental results showed, the actual effects of pulsed operation are more complicated. Reference 6 discusses simulations of the output of GaAs concentrator solar cells under pulsed laser illumination. The present paper continues this work, and compares the output of Si and GaAs solar cells.
Jain, Raj K.; Landis, Geoffrey A.
Thermodynamic Efficiency Limits for Optically Boosted Planar Solar Cells
NASA Astrophysics Data System (ADS)
Recent attempts have been made to convert the broadband solar spectrum into filtered light, for the purpose of boosting the efficiency of a planar solar cell. By developing a thermodynamic model, the rigorous efficiency limits of the optically boosted solar cells are presented, which are achievable in principle with a piecewise function of the front emissivity or the energy-redistribution lifetime.
Feng, Y.; Shrestha, S.; Huang, S.; Conibeer, G.
Dielectric nanostructures for broadband light trapping in organic solar cells
generation. © 2011 Optical Society of America OCIS codes: (350.6050) Solar energy; (350.4238) Nanophotonics solar cells," Nano Lett. 9, 27422746 (2009). 12. E. Yablonovitch, "Statistical ray optics," J. Opt. SocDielectric nanostructures for broadband light trapping in organic solar cells Aaswath Raman, Zongfu
Fan, Shanhui
Characterization testing of Intelsat VI solar cell assemblies
A complete characterization program has been performed on the two solar cell types which will be used on the Intelsat VI solar arrays. Each cell type was subjected to a series of tests which (1) provided the data needed to accurately predict the solar array performance at end of life, and (2) demonstrated the mechanical integrity of the devices. Characterization
J. S. Fodor; S. W. Gelb; L. J. Goldhammer; G. S. Goodelle
WORKING QUANTUM EFFICIENCY OF CDTE SOLAR CELL Zimeng Cheng
, the quantum efficiency of CdTe solar cell with various optical biases, which is titled as "Working Quantum Chen 1 , Tao Zhou 2 , Qi Wang 3 , George E. Georgiou 1 , Ken K. Chin 1 1 Apollo CdTe Solar Energy Renewable Energy Laboratory (NREL), Golden, CO 80401 USA ABSTRACT For p-CdTe/n-CdS solar cell
Transcending QCD in Nanostructured Solar Cells G. Galli S. Kauzlarich
(2012), 31% (2013) (Alta Devices) - Thin films: 19% in CdTe (2013) (First Solar) - Organic solar cells Optimization of gap: max efficiency: 31% (Shockley Queisser 1961) In real PV cells 80-85% of incident solar efficiency: 44% 1 Sun (Klimov 2005) 70% 1000 Sun (Nozik 2013) doubled current E g h v oltage e h Keep
Squaraine donor based organic solar cells
NASA Astrophysics Data System (ADS)
There are three main ongoing avenues to improve the power conversion efficiency of organic photovoltaics (OPV): the development of new organic materials, improved process control and novel device architecture design. In this thesis, through molecular design with chemical modification of functional organic molecules, a family of new highly absorptive solution processable squaraine (SQ) materials have been systematically synthesized and explored to improve the sunlight harvesting and charge transport. The spin-cast SQ donors are then coated with fullerene acceptors to form a unique nanocrystalline heterojunction (NcHJ) OPV device. This combination of a novel and efficient family of SQ donors, a unique NcHJ device architecture and optimized fabrication processes leads to high efficiency solar cells. For example, solar cells with efficiencies of �5.7 % and a fill factor �0.74 are achieved. We find a correlation between solar cell fill factor with the SQ thin film density, providing support for the molecular design concept that planar end groups result in close intermolecular stacking, and hence improved charge transport and exciton diffusion. Finally, thermal annealing of the films results in the formation of nanocrystalline morphologies that lead to further improvements in device performance. The microcrystal growth of SQ donors have been characterized by XRD, AFM and TEM.
Wei, Guodan
Oxide nanowires for solar cell applications.
Oxide nanowire arrays were studied for their applications to solar cells. It was demonstrated that the nanowires could provide direct pathways for electron transport in dye-sensitized solar cells and therefore, while forming photoelectrode films, they offered better suppression of charge recombination than nanoparticles. However, the photoelectron films consisting of nanowires suffered a disadvantage in giving large surface area for dye adsorption. Such a shortcoming of nanowires had been exemplified in this paper illustrating that it could be well compensated by incorporating with nanoparticles to form a nanoparticle-nanowire array hybrid photoelectrode film. The oxide nanowires were also demonstrated to be able to enhance the performance of inverted structure polymer solar cells as a cathode buffer layer by establishing a large interface with the polymers so as to facilitate the transport of photogenerated electrons from the polymer to the electron collecting electrode. Such an enhancement effect could be further boosted while the nanowires were replaced with nanotubes; the latter may build up larger interface with the polymers than the former and therefore facilitates the electron transport more efficiently. PMID:22200055
Zhang, Qifeng; Yodyingyong, Supan; Xi, Junting; Myers, Daniel; Cao, Guozhong
(abstract) Scaling Nominal Solar Cell Impedances for Array Design
NASA Technical Reports Server (NTRS)
This paper discusses a task the objective of which is to characterize solar cell array AC impedance and develop scaling rules for impedance characterization of large arrays by testing single solar cells and small arrays. This effort is aimed at formulating a methodology for estimating the AC impedance of the Mars Pathfinder (MPF) cruise and lander solar arrays based upon testing single cells and small solar cell arrays and to create a basis for design of a single shunt limiter for MPF power control of flight solar arrays having very different inpedances.
Mueller, Robert L; Wallace, Matthew T.; Iles, Peter
NASA Technical Reports Server (NTRS)
The AstroPower self-supporting, transparent AlGaAs top solar cell can be stacked upon any well-developed bottom solar cell for improved system performance. This is an approach to improve the performance and scale of space photovoltaic power systems. Mechanically stacked tandem solar cell concentrator systems based on the AlGaAs top concentrator solar cell can provide near term efficiencies of 36 percent (AMO, 100x). Possible tandem stack efficiencies greater than 38 percent (100x, AMO) are feasible with a careful selection of materials. In a three solar cell stack, system efficiencies exceed 41 percent (100x, AMO). These device results demonstrate a practical solution for a state-of-the-art top solar cell for attachment to an existing, well-developed solar cell.
Dinetta, L. C.; Hannon, M. H.; Mcneely, J. B.; Barnett, A. M.
CLEFT Process for GaAs Solar Cells
NASA Technical Reports Server (NTRS)
CLEFT (cleavage of lateral epitaxial films for transfer) process involves growing ultrathin gallium arsenide (GaAs solar cell on much thicker layer of same material). Growth method is completed solar cell easily separated by cleaving from much thicker substrate. Thick substrate is reusable in making additional cells, which reduces cell material cost.
Fan, J. C. C.; Bozler, C. O.; Mcclelland, R. W.
Modeling the Effects of Solar Cell Distribution on Optical Cross Section for Solar Panel Simulation.
National Technical Information Service (NTIS)
The Air Force Research Laboratory (AFRL) Time-domain Analysis Simulation for Advanced Tracking (TASAT) was used to explore the variation of Optical Cross Section (OCS) with glint angle for a solar panel with different solar cell distribution statistics. S...
K. Feirstine, L. Vaughn, M. Duggin, M. Klein
Epitaxial solar-cell fabrication, phase 2
NASA Technical Reports Server (NTRS)
Dichlorosilane (SiH2Cl2) was used as the silicon source material in all of the epitaxial growths. Both n/p/p(+) and p/n/n(+) structures were studied. Correlations were made between the measured profiles and the solar cell parameters, especially cell open-circuit voltage. It was found that in order to obtain consistently high open-circuit voltage, the epitaxial techniques used to grow the surface layer must be altered to obtain very abrupt doping profiles in the vicinity of the junction. With these techniques, it was possible to grow reproducibly both p/n/n(+) and n/p/p(+) solar cell structures having open-circuit voltages in the 610- to 630-mV range, with fill-factors in excess of 0.80 and AM-1 efficiencies of about 13%. Combinations and comparisons of epitaxial and diffused surface layers were also made. Using such surface layers, we found that the blue response of epitaxial cells could be improved, resulting in AM-1 short-circuit current densities of about 30 mA/cm sq. The best cells fabricated in this manner had AM-1 efficiency of 14.1%.
Daiello, R. V.; Robinson, P. H.; Kressel, H.
SAGE: Solar Neutrino Data from SAGE, the Russian-American Gallium Solar Neutrino Experiment
SAGE is a solar neutrino experiment based on the reaction 71Ga + n goes to 71Ge + e-. The 71Ge atoms are chemically extracted from a 50-metric ton target of Ga metal and concentrated in a sample of germane gas mixed with xenon. The atoms are then individually counted by observing their decay back to 71Ga in a small proportional counter. The distinguishing feature of the experiment is its ability to detect the low-energy neutrinos from proton-proton fusion. These neutrinos, which are made in the primary reaction that provides the Sun's energy, are the major component of the solar neutrino flux and have not been observed in any other way. To shield the experiment from cosmic rays, it is located deep underground in a specially built facility at the Baksan Neutrino Observatory in the northern Caucasus mountains of Russia. Nearly 100 measurements of the solar neutrino flux have been made during 1990-2000, and their combined result is a neutrino capture rate that is well below the prediction of the Standard Solar Model. The significant suppression of the solar neutrino flux that SAGE and other solar neutrino experiments have observed gives a strong indication for the existence of neutrino oscillations. [copied from the SAGE homepage at http://ewi.npl.washington.edu/SAGE/SAGE.html
SAGE Collaboration
15 cm�15 cm high efficiency multicrystalline silicon solar cell
A large-area multicrystalline silicon solar cell with 15 cm�15 cm cell area using a substrate made by a casting method has been developed to obtain high efficiency at low cost. The bifacial silicon nitride solar cell (BSNSC) fabrication process has been applied to this large-area solar cell. By optimizing the surface structure to reduce the reflective losses, the p-n junction
K. Fukui; H. Yamashita; M. Takayama; K. Okada; K. Masuri; K. Shirasawa; H. Watanabe
Evaluation of concentration solar cells for terrestrial applications
Solar energy has become a hot prospect for the future replacement of fossil fuels, which have limited reserves and cause environmental problems. Solar cell is such a device to directly generate electricity from this clean ...
An, Tao, M. Eng. Massachusetts Institute of Technology
Defect behavior of polycrystalline solar cell silicon
The major objective of this study, conducted from October 1988 to September 1991, was to gain an understanding of the behavior of impurities in polycrystalline silicon and the influence of these impurities on solar cell efficiency. The authors studied edge-defined film-fed growth (EFG) and cast poly-Si materials and solar cells. With EFG Si they concentrated on chromium-doped materials and cells to determine the role of Cr on solar cell performance. Cast poly-Si samples were not deliberately contaminated. Samples were characterized by cell efficiency, current-voltage, deep-level transient spectroscopy (DLTS), surface photovoltage (SPV), open-circuit voltage decay, secondary ion mass spectrometry, and Fourier transform infrared spectroscopy measurements. They find that Cr forms Cr-B pairs with boron at room temperature and these pairs dissociate into Cr{sub i}{sup +} and B{sup {minus}} during anneals at 210{degrees}C for 10 min. Following the anneal, Cr-B pairs reform at room temperature with a time constant of 230 h. Chromium forms CrSi{sub 2} precipitates in heavily contaminated regions and they find evidence of CrSi{sub 2} gettering, but a lack of chromium segregation or precipitation to grain boundaries and dislocations. Cr-B pairs have well defined DLTS peaks. However, DLTS spectra of other defects are not well defined, giving broad peaks indicative of defects with a range of energy levels in the band gap. In some high-stress, low-efficiency cast poly-Si they detect SiC precipitates, but not in low-stress, high-efficiency samples. SPV measurements result in nonlinear SPV curves in some materials that are likely due to varying optical absorption coefficients due to locally varying stress in the material.
Schroder, D.K.; Park, S.H.; Hwang, I.G.; Mohr, J.B.; Hanly, M.P. [Arizona State Univ., Tempe, AZ (US). Center for Solid State Electronics Research
Solar cell angle of incidence corrections
NASA Technical Reports Server (NTRS)
Literature on solar array angle of incidence corrections was found to be sparse and contained no tabular data for support. This lack along with recent data on 27 GaAs/Ge 4 cm by 4 cm cells initiated the analysis presented in this paper. The literature cites seven possible contributors to angle of incidence effects: cosine, optical front surface, edge, shadowing, UV degradation, particulate soiling, and background color. Only the first three are covered in this paper due to lack of sufficient data. The cosine correction is commonly used but is not sufficient when the incident angle is large. Fresnel reflection calculations require knowledge of the index of refraction of the coverglass front surface. The absolute index of refraction for the coverglass front surface was not known nor was it measured due to lack of funds. However, a value for the index of refraction was obtained by examining how the prediction errors varied with different assumed indices and selecting the best fit to the set of measured values. Corrections using front surface Fresnel reflection along with the cosine correction give very good predictive results when compared to measured data, except there is a definite trend away from predicted values at the larger incident angles. This trend could be related to edge effects and is illustrated by a use of a box plot of the errors and by plotting the deviation of the mean against incidence angle. The trend is for larger deviations at larger incidence angles and there may be a fourth order effect involved in the trend. A chi-squared test was used to determine if the measurement errors were normally distributed. At 10 degrees the chi-squared test failed, probably due to the very small numbers involved or a bias from the measurement procedure. All other angles showed a good fit to the normal distribution with increasing goodness-of-fit as the angles increased which reinforces the very small numbers hypothesis. The contributed data only went to 65 degrees from normal which prevented any firm conclusions about extreme angle effects although a trend in the right direction was seen. Measurement errors were estimated and found to be consistent with the conclusions that were drawn. A controlled experiment using coverglasses and cells from the same lots and extending to larger incidence angles would probably lead to further insight into the subject area.
Burger, Dale R.; Mueller, Robert L.
Solar-Stellar Irradiance Comparison Experiment 1. II - Instrument calibrations
NASA Technical Reports Server (NTRS)
The science objective for the Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) is to accurately measure the full disk solar spectral irradiance in the ultraviolet (UV) spectral region over a long time period. The SOLSTICE design was driven by the requirement for long-term, precise solar photometry conducted from space. The SOLSTICE 1 is on the Upper Atmosphere Research Satellite (UARS), launched in September 1991 with the possibility for a 10-year operational mission. The in-flight calibration for SOLSTICE to meet its primary objective is the routine measurements of the UV radiation from a set of early-type stars, using the identical optical elements employed for the solar observations. The extensive preflight calibrations of the instrument have yielded a precise characterization of the three SOLSTICE channels. Details of the preflight and in-flight SOLSTICE calibrations are discussed in this paper.
Woods, Thomas N.; Rottman, Gary J.; Ucker, Gregory J.
VIRGO: Experiment for helioseismology and solar irradiance monitoring
NASA Technical Reports Server (NTRS)
The scientific objectives of the variability of solar irradiance and gravity oscillations (VIRGO) experiment are as follows: to determine the characteristics of pressure and internal gravity oscillations by observing irradiance and radiance variations; to measure the solar total and spectral irradiance, and to quantify their variability. Helioseismological methods can be applied to these data in order to probe the solar interior. Certain convection characteristics and their interaction with magnetic fields will be studied from the results of the irradiance monitoring and from the comparison of the amplitudes and phases of the oscillations as observed from the brightness by VIRGO and from velocity by the global oscillations at low frequency (GOLF) experiment. The VIRGO experiment contains two active-cavity radiometers that monitor the solar constant, two three-channel sunphotometers that measure the spectral irradiance, and a low resolution imager with 12 pixels that measures the radiance distribution over the solar disk at 500 nm. The scientific objectives of VIRGO are presented, the instruments and the data acquisition and control system are described, and their measured performances are given.
Froehlich, Claus; Andersen, Bo N.
A Simple and Inexpensive Solar Energy Experiment.
ERIC Educational Resources Information Center
An experiment is presented which utilizes the current solid state technology to demonstrate electrochemical generation of hydrogen gas, direct generation of electricity for pumping water, and energy conversion efficiency. The experimental module costs about $100 and can be used repeatedly. (BB)
Evans, J. H.; Pedersen, L. G.
Radiation tolerance of low resistivity, high voltage silicon solar cells
NASA Technical Reports Server (NTRS)
The radiation tolerance of the following three low resistivity, high voltage silicon solar cells was investigated: (1) the COMSAT MSD (multi-step diffused) cell, (2) the MinMIS cell, and (3) the MIND cell. A description of these solar cells is given along with drawings of their configurations. The diffusion length damage coefficients for the cells were calculated and presented. Solar cell spectral response was also discussed. Cells of the MinMIS type were judged to be unsuitable for use in the space radiation environment.
Weizer, V. G.; Weinberg, I.; Swartz, C. K.
Materials That Enhance Efficiency and Radiation Resistance of Solar Cells
NASA Technical Reports Server (NTRS)
A thin layer (approximately 10 microns) of a novel "transparent" fluorescent material is applied to existing solar cells or modules to effectively block and convert UV light, or other lower solar response waveband of solar radiation, to visible or IR light that can be more efficiently used by solar cells for additional photocurrent. Meanwhile, the layer of fluorescent coating material remains fully "transparent" to the visible and IR waveband of solar radiation, resulting in a net gain of solar cell efficiency. This innovation alters the effective solar spectral power distribution to which an existing cell gets exposed, and matches the maximum photovoltaic (PV) response of existing cells. By shifting a low PV response waveband (e.g., UV) of solar radiation to a high PV response waveband (e.g. Vis-Near IR) with novel fluorescent materials that are transparent to other solar-cell sensitive wavebands, electrical output from solar cells will be enhanced. This approach enhances the efficiency of solar cells by converting UV and high-energy particles in space that would otherwise be wasted to visible/IR light. This innovation is a generic technique that can be readily implemented to significantly increase efficiencies of both space and terrestrial solar cells, without incurring much cost, thus bringing a broad base of economical, social, and environmental benefits. The key to this approach is that the "fluorescent" material must be very efficient, and cannot block or attenuate the "desirable" and unconverted" waveband of solar radiation (e.g. Vis-NIR) from reaching the cells. Some nano-phosphors and novel organometallic complex materials have been identified that enhance the energy efficiency on some state-of-the-art commercial silicon and thin-film-based solar cells by over 6%.
Sun, Xiadong; Wang, Haorong
Quantum Dots Investigated for Solar Cells
NASA Technical Reports Server (NTRS)
The NASA Glenn Research Center has been investigating the synthesis of quantum dots of CdSe and CuInS2 for use in intermediate-bandgap solar cells. Using quantum dots in a solar cell to create an intermediate band will allow the harvesting of a much larger portion of the available solar spectrum. Theoretical studies predict a potential efficiency of 63.2 percent, which is approximately a factor of 2 better than any state-of-the-art devices available today. This technology is also applicable to thin-film devices--where it offers a potential four-fold increase in power-to-weight ratio over the state of the art. Intermediate-bandgap solar cells require that quantum dots be sandwiched in an intrinsic region between the photovoltaic solar cell's ordinary p- and n-type regions (see the preceding figure). The quantum dots form the intermediate band of discrete states that allow sub-bandgap energies to be absorbed. However, when the current is extracted, it is limited by the bandgap, not the individual photon energies. The energy states of the quantum dot can be controlled by controlling the size of the dot. Ironically, the ground-state energy levels are inversely proportional to the size of the quantum dots. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Ba Wendi et al., in the early 1990's. The most studied quantum dots prepared by this method have been of CdSe. To produce these dots, researchers inject a syringe of the desired organometallic precursors into heated triocytlphosphine oxide (TOPO) that has been vigorously stirred under an inert atmosphere (see the following figure). The solution immediately begins to change from colorless to yellow, then orange and red/brown, as the quantum dots increase in size. When the desired size is reached, the heat is removed from the flask. Quantum dots of different sizes can be identified by placing them under a "black light" and observing the various color differences in their fluorescence (see the photograph).
Bailey, Sheila G.; Castro, Stephanie L.; Raffaelle, Ryne P.; Hepp, Aloysius F.
Todays solar cells are fabricated using metal oxide based transparent conductive coatings (TCC) or metal wires with optoelectronic performance exceeding that currently possible with Carbon Nanotube (CNT) based TCCs. The motivation for replacing current TCC is their inherent brittleness, high deposition cost, and high deposition temperatures; leading to reduced performance on thin substrates. With improved processing, application and characterization techniques Nanofiber and/or CNT based TCCs can overcome these shortcomings while offering the ability to be applied in atmospheric conditions using low cost coating processes At todays level of development, CNT based TCC are nearing commercial use in touch screens, some types of information displays (i.e. electronic paper), and certain military applications. However, the resistivity and transparency requirements for use in current commercial solar cells are more stringent than in many of these applications. Therefore, significant research on fundamental nanotube composition, dispersion and deposition are required to reach the required performance commanded by photovoltaic devices. The objective of this project was to research and develop transparent conductive coatings based on novel nanomaterial composite coatings, which comprise nanotubes, nanofibers, and other nanostructured materials along with binder materials. One objective was to show that these new nanomaterials perform at an electrical resistivity and optical transparency suitable for use in solar cells and other energy-related applications. A second objective was to generate new structures and chemistries with improved resistivity and transparency performance. The materials also included the binders and surface treatments that facilitate the utility of the electrically conductive portion of these composites in solar photovoltaic devices. Performance enhancement venues included: CNT purification and metallic tube separation techniques, chemical doping, CNT patterning and alignment, advances in commercial and research materials and field effect schemes. In addition, Eikos continued to develop improved efficiency coating materials and transfer methods suitable for batch and continuous roll-to-roll fabrication requirements. Finally, Eikos collaborated with NREL and the PV-community at large in fabricating and characterizing Invisicon�?�?�?® enabled solar cells.
Glatkowski, P.J.; Landis, D.A.
NASA Technical Reports Server (NTRS)
For the March/April 1991 time period, the alpha/proton abundance ratio, the proton kinetic temperature and speed distributions, and the relative abundance of O(+7) to O(+6) is determined over each 13-minute duty cycle of the Solar Wind Ion Composition Spectrometer (SWICs) experiment on Ulysses. The ratio O(+7)/O(+6) (as a relative measure of ionization temperature) is shown to be useful in identifying possible coronal mass ejection (CME) events. We report measurements of silicon/oxygen abundance ratios and silicon and oxygen charge state distributions in the solar wind during a CME event and compare these compositions to a 'normal' solar wind time period.
Galvin, A. B.; Gloeckler, G.; Ipavich, F. M.; Shafer, C. M.; Geiss, J.; Ogilvie, K.
NASA Astrophysics Data System (ADS)
Micron-scale Si wire arrays are three-dimensional photovoltaic absorbers that enable orthogonalization of light absorption and carrier collection and hence allow for the utilization of relatively impure Si in efficient solar cell designs. The wire arrays are grown by a vapor-liquid-solid-catalyzed process on a crystalline (111) Si wafer lithographically patterned with an array of metal catalyst particles. Following growth, such arrays can be embedded in polymethyldisiloxane (PDMS) and then peeled from the template growth substrate. The result is an unusual photovoltaic material: a flexible, bendable, wafer-thickness crystalline Si absorber. In this paper I will describe: 1. the growth of high-quality Si wires with controllable doping and the evaluation of their photovoltaic energy-conversion performance using a test electrolyte that forms a rectifying conformal semiconductor-liquid contact 2. the observation of enhanced absorption in wire arrays exceeding the conventional light trapping limits for planar Si cells of equivalent material thickness and 3. single-wire and large-area solid-state Si wire-array solar cell results obtained to date with directions for future cell designs based on optical and device physics. In collaboration with Michael Kelzenberg, Morgan Putnam, Joshua Spurgeon, Daniel Turner-Evans, Emily Warren, Nathan Lewis, and Harry Atwater, California Institute of Technology.
Boettcher, Shannon
A theoretical analysis of the current-voltage characteristics of solar cells
NASA Technical Reports Server (NTRS)
The following topics are discussed: (1) dark current-voltage characteristics of solar cells; (2) high efficiency silicon solar cells; (3) short circuit current density as a function of temperature and the radiation intensity; (4) Keldysh-Franz effects and silicon solar cells; (5) thin silicon solar cells; (6) optimum solar cell designs for concentrated sunlight; (7) nonuniform illumination effects of a solar cell; and (8) high-low junction emitter solar cells.
Fang, R. C. Y.; Hauser, J. R.
The 1-kW solar Stirling experiment
NASA Astrophysics Data System (ADS)
The objective of this experiment was to demonstrate electrical power generation using a small free-piston Stirling engine and linear alternator in conjunction with a parabolic solar collector. A test bed collector, formerly used at the JPL Table Mountain Observatory, was renovated and used to obtain practical experience and to determine test receiver performance. The collector was mounted on a two-axis tracker, with a cold water calorimeter mounted on the collector to measure its efficiency, while a separate, independently tracking radiometer was used to measure solar insolation. The solar receiver was designed to absorb energy from the collector, then transfer the resulting thermal energy to the Stirling engine. Successful testing of receiver/collector assembly yielded valuable inputs for design of the Stirling engine heater head.
Giandomenico, A.
Solar energy: Lessons from the Pacific island experience
NASA Astrophysics Data System (ADS)
The experiences of several Pacific island countries provides a clear indication that in small, remote villages, off-the-shelf solar photovoltaic (PV) technologies are providing reliable power at costs less than those of the more commonly used diesel systems for households running a few electric lights and a TV/VCR. The report also confirms another point made repeatedly in the authors' recent energy sector work: appropriate technical choices need to be complemented by effective institutional approaches. The Pacific island experience demonstrated that the success of solar PV programs depended not merely on the choice of technology but on adequate training of maintenance personnel, good fee collection systems, and careful financial management. The report indicates that for solar PV systems installed in areas where managerial and technical expertise is scarce, ownership and maintenance of the systems by local, cooperatively owned utilities appears to be the soundest option.
Liebenthal, A.; Mathur, S.; Wade, H.
Investigating the efficiency of Silicon Solar cells at
to study the characteristics of silicon photovoltaic cells (solar cells). We vary the wavelength of light when leads are attached to the opposite sides of this p-n junction. In photovoltaic cells, the energy
Attari, Shahzeen Z.
High efficiency, radiation-hard solar cells
The direct gap of the In{sub 1-x}Ga{sub x}N alloy system extends continuously from InN (0.7 eV, in the near IR) to GaN (3.4 eV, in the mid-ultraviolet). This opens the intriguing possibility of using this single ternary alloy system in single or multi-junction (MJ) solar cells of the type used for space-based surveillance satellites. To evaluate the suitability of In{sub 1-x}Ga{sub x}N as a material for space applications, high quality thin films were grown with molecular beam epitaxy and extensive damage testing with electron, proton, and alpha particle radiation was performed. Using the room temperature photoluminescence intensity as a indirect measure of minority carrier lifetime, it is shown that In{sub 1-x}Ga{sub x}N retains its optoelectronic properties at radiation damage doses at least 2 orders of magnitude higher than the damage thresholds of the materials (GaAs and GaInP) currently used in high efficiency MJ cells. This indicates that the In{sub 1-x}Ga{sub x}N is well-suited for the future development of ultra radiation-hard optoelectronics. Critical issues affecting development of solar cells using this material system were addressed. The presence of an electron-rich surface layer in InN and In{sub 1-x}Ga{sub x}N (0 < x < 0.63) was investigated; it was shown that this is a less significant effect at large x. Evidence of p-type activity below the surface in Mg-doped InN was obtained; this is a significant step toward achieving photovoltaic action and, ultimately, a solar cell using this material.
Ager III, J.W.; Walukiewicz, W.
Investigation of planar antennas with photovoltaic solar cells for mobile communications
This paper describes the application of photovoltaic (PV) solar cells in planar antenna structures. The radiating patch element of a planar antenna is replaced by a solar cell. Furthermore radiating slots are built due to the cell spacing in a solar cell array. The original feature of a solar cell (DC current generation) remains, but additionally the solar cell is
Norbert Henze; Martin Weitz; Pascal Hofmann; Christian Bendel; J�rg Kirchhof; Henning Friichtingl
NASA Technical Reports Server (NTRS)
The conceptual equipment and techniques for fabricating and assembling a ladder-like structure of triangular cross section trusses suitable for mounting solar cell arrays are described. The detail information is presented in the context of a proposed experiment to be conducted from the shuttle in the 1980-84 time period as an early experiment in the development of techniques for the construction of large space structures that would be required for space solar power stations and other large systems.
Plasma-enhanced CVD silicon nitride antireflection coatings for solar cells
NASA Technical Reports Server (NTRS)
Multilayer plasma-enhanced chemical vapor deposition (PECVD) silicon nitride antireflection coatings were deposited on space quality silicon solar cells. Preliminary experiments indicated that multilayer coatings decreased the total reflectance of polished silicon from 35 percent to less than 3 percent over the spectral range 0.4-1.0 micron. The solar cell energy conversion efficiency was increased from an average of 8.84 percent to an average of 12.63 percent.
Johnson, C. C.; Wydeven, T.; Donohoe, K.
Practical high efficiency bifacial solar cells
In this paper, the authors present a practical process to obtain bifacial solar cells. These cells are made using p{sup +}nn{sup +} structure on high-medium base resistivity, continuous emitters and with a process that maintains high bulk minority carrier lifetime. Efficiencies of 19.1% and 18.1% are achieved under standard conditions when the cell is illuminated by n{sup +}n high-low junction and when it is illuminated by P{sup +}n junction, respectively. The authors remark that the n{sup +}n high-low junction provides a higher current density and a good ratio between generated current of each face is found to be of about 103%.
Moehlecke, A.; Zanesco, I.; Luque, A. [ETSI Telecomunicacion, Madrid (Spain). Inst. de Energia Solar
NASA Technical Reports Server (NTRS)
Photovoltaic cells (solar cells) and other solar array materials were flown in a variety of locations on the Long Duration Exposure Facility (LDEF). With respect to the predicted leading edge, solar array experiments were located at 0 degrees (row 9), 30 degrees (row 8) and 180 degrees (row 3). Postflight estimates of location of the experiments with respect to the velocity vector add 8.1 degrees to these values. Experiments were also located on the Earth end of the LDEF longitudinal axis. Types and magnitudes of detrimental effects differ between the locations with some commonality. Postflight evaluation of the solar array experiments reveal that some components/materials are very resistant to the environment to which they were exposed while others need protection, modification, or replacement. Interaction of materials with atomic oxygen (AO), as an area of major importance, was dramatically demonstrated by LDEF results. Information gained from the LDEF flight allows array developers to set new requirements for on-going and future technology and flight component development.
Young, Leighton E.
Solare Cell Roof Tile And Method Of Forming Same
A solar cell roof tile includes a front support layer, a transparent encapsulant layer, a plurality of interconnected solar cells and a backskin layer. The front support layer is formed of light transmitting material and has first and second surfaces. The transparent encapsulant layer is disposed adjacent the second surface of the front support layer. The interconnected solar cells has a first surface disposed adjacent the transparent encapsulant layer. The backskin layer has a first surface disposed adjacent a second surface of the interconnected solar cells, wherein a portion of the backskin layer wraps around and contacts the first surface of the front support layer to form the border region. A portion of the border region has an extended width. The solar cell roof tile may have stand-offs disposed on the extended width border region for providing vertical spacing with respect to an adjacent solar cell roof tile.
Hanoka, Jack I. (Brookline, MA); Real, Markus (Oberberg, CH)
A dry vapor treatment of CdCl2 is being developed as an alternative approach to the conventional solution CdCl2 treatment of CdS/CdTe devices. In this alternative process, the CdS/CdTe substrates are vapor treated in a close-spaced sublimation configuration. A 16-run Plackett-Burman screening experiment identified source temperature, substrate temperature, and treatment time as being the most significant parameters in the process. Subsequently, a 20-run Central Composite Design showed that a source temperature of 380-390 C, a temperature gradient (DT) of 5 C, and a time of 10 minutes provides the most process tolerant combination, yielding a total-area efficiency of 12.6%. A strong interaction between DT and treatment time was also identified. The model indicated that for a small DT, device performance improved with decreasing time, whereas at larger values of DT, performance increased with increasing time.
Mahathongdy, Y.; Wolden, C. A.; Baldwin, R. M. (Colorado School of Mines, Golden, CO); Albin, D. S. (National Renewable Energy Laboratory)
Characterization of production GaAs solar cells for space
NASA Technical Reports Server (NTRS)
The electrical performance of GaAs solar cells was characterized as a function of irradiation with protons and electrons with the underlying goal of producing solar cells suitable for use in space. Proton energies used varied between 50 keV and 10 MeV, and damage coefficients were derived for liquid phase epitaxy GaAs solar cells. Electron energies varied between 0.7 and 2.4 MeV. Cells from recent production runs were characterized as a function of electron and proton irradiation. These same cells were also characterized as a function of solar intensity and operating temperature, both before and after the electron irradiations. The long term stability of GaAs cells during photon exposure was examined. Some cells were found to degrade with photon exposure and some did not. Calibration standards were made for GaAs/Ge solar cells by flight on a high altitude balloon.
Anspaugh, B. E.
Use of photovoltage for electrodeposition in solar cell processing technology
This paper reports the development of a new technology for the electrolytic deposition of a metal on a solar cell, without employing an external electric bias field, but by using the internal photo-induced voltage of the solar cell itself. The experimental details of depositing silver over the existing metallized contact structure of the cell and a transparent conducting oxide coating
V. K. Jain; A. R. Kulshreshtha
Applications of ion implantation for high efficiency silicon solar cells
NASA Technical Reports Server (NTRS)
Ion implantation is utilized for the dopant introduction processes necessary to fabricate a silicon solar cell. Implantation provides a versatile powerful tool for development of high efficiency cells. Advantages and problems of implantation and the present status of developmental use of the technique for solar cells are discussed.
Minnucci, J. A.; Kirkpatrick, A. R.
EELE408 Photovoltaics Lecture 10 Solar Cell Operation
-generated carriers to generate a current · The generation of a voltage across the solar cell · The dissipation generated current · Red Light (0.8 m) = 103/cm Absorbed deeper in cell · Infrared Light (1.1 m) = 101/cm of the number of carriers collected by the solar cell to the number of photons of a given energy incident
Kaiser, Todd J.
High efficiency solar cell arrays system trade-offs
Advanced high efficiency GaAs\\/Ge solar cells are now being manufactured in large quantities and are being utilized on many spacecraft. Since the bare solar cell cost and efficiency is much higher than silicon cells, it is often difficult to determine the system cost advantages that are hard to quantify in terms of cost benefits. In order to provide some guidance
E. L. Ralph
Laser processes for future solar cells
NASA Astrophysics Data System (ADS)
The photovoltaic (PV) industry requires higher efficiencies at lower manufacturing costs to become competitive with other power generation techniques. There are several approaches to increase the efficiency of solar cells. For example enhancements of the way photons are absorbed and how they generate charge carriers with low losses. Today, the so called first generation of photovoltaic devices based on crystalline silicon wafers are produced on a multi-GW-level. However, in most production lines there is only one laser process used to electrically isolate front and rear side of the cell. Lasers are predestined to generate local structures which will be required to manufacture high efficient solar cells. As an example we will show results on the interaction of ultra short laser pulses with dielectric films on silicon. Second generation photovoltaic modules are based on thin films. These modules are monolithically interconnected by laser scribing of the films. Tools for amorphous silicon are well established, while there are a lot of challenges to scribe CIGS layers. Within this paper we will show new results on the temporal evolution of a laser induced "lift-off" process to scribe the molybdenum back electrode.
Letsch, Andreas; Bartl, Dominik; Diez, Michael; Gauch, Roland; Michalowski, Andreas; Hafner, Margit
Effective Interfaces in Silicon Heterojunction Solar Cells
This paper reviews the current commercial status of CuInSe2 alloys (collectively, CIS) and CdTe-based photovoltaic (PV) modules, comparing the performance of commercial products with the results achieved for solar cell and prototype module champions. We provide an update for these PV cell and module technologies, and also compare CIS and CdTe performance levels to the results achieved by the crystalline Si PV industry. This comparison shows that CIS and CdTe module technology presently offers the best (and perhaps only) approach for significantly exceeding the cost/performance levels established by crystalline Si PV technologies. A semi-empirical methodology is used for comparing ''champion'' solar cell and prototype module data with performance achieved on manufacturing lines. Using a conservative assumption that thin-film technologies will eliminate the 40% of PV module costs arising from the Si wafer or ribbon, we estimate the future performance of all established PV module candidates, and conclude that, based on 2004 knowledge about each PV technology, CIS and CdTe should provide cost-competitive advantages over crystalline Si.
Wang, T. H.; Iwaniczko, E.; Page, M. R.; Levi, D. H.; Yan, Y.; Yelundur, V.; Branz, H. M.; Rohatgi, A.; Wang, Q.
Material and processing needs for silicon solar cells in space
NASA Technical Reports Server (NTRS)
The technical concerns of NASA in the area of space grade solar cells are summarized. Solar power needs are projected through 1987. The degradation of solar cell performance due to the effects of radiation on impurities and crystal defects and the improved performance of float zone silicon are illustrated. The reduction of oxygen and carbon in float zone silicon allows for much faster low temperature annealing of the defects. The effects of improved crystal purity on cell performance are summarized.
Brandhorst, H. W., Jr.
Spraylon fluorocarbon encapsulation for silicon solar cell arrays
NASA Technical Reports Server (NTRS)
A development program was performed for evaluating, modifying, and optimizing the Lockheed formulated liquid transparent filmforming Spraylon fluorocarbon protective coating for silicon solar cells and modules. The program objectives were designed to meet the requirements of the low-cost automated solar cell array fabrication process. As part of the study, a computer program was used to establish the limits of the safe working stress in the coated silicon solar cell array system under severe thermal shock.
Shunt effect in polycrystalline GaAs solar cells
Thin-film polycrystalline GaAs solar cells have the potential for reduced cost while retaining high efficiency. However, solar cells made from polycrystalline GaAs have historically had poor open-circuit voltages. Models that account for these low voltages suggest that in order to make solar cells with high voltages it is necessary to use material with very large grains. As an alternative cause
Christiana Honsberg; Allen M. Bernett
Elongated nanostructures for radial junction solar cells.
In solar cell technology, the current trend is to thin down the active absorber layer. The main advantage of a thinner absorber is primarily the reduced consumption of material and energy during production. For thin film silicon (Si) technology, thinning down the absorber layer is of particular interest since both the device throughput of vacuum deposition systems and the stability of the devices are significantly enhanced. These features lead to lower cost per installed watt peak for solar cells, provided that the (stabilized) efficiency is the same as for thicker devices. However, merely thinning down inevitably leads to a reduced light absorption. Therefore, advanced light trapping schemes are crucial to increase the light path length. The use of elongated nanostructures is a promising method for advanced light trapping. The enhanced optical performance originates from orthogonalization of the light's travel path with respect to the direction of carrier collection due to the radial junction, an improved anti-reflection effect thanks to the three-dimensional geometric configuration and the multiple scattering between individual nanostructures. These advantages potentially allow for high efficiency at a significantly reduced quantity and even at a reduced material quality, of the semiconductor material. In this article, several types of elongated nanostructures with the high potential to improve the device performance are reviewed. First, we briefly introduce the conventional solar cells with emphasis on thin film technology, following the most commonly used fabrication techniques for creating nanostructures with a high aspect ratio. Subsequently, several representative applications of elongated nanostructures, such as Si nanowires in realistic photovoltaic (PV) devices, are reviewed. Finally, the scientific challenges and an outlook for nanostructured PV devices are presented. PMID:24088584
Kuang, Yinghuan; Vece, Marcel Di; Rath, Jatindra K; Dijk, Lourens van; Schropp, Ruud E I
Photon management structures for solar cells
NASA Astrophysics Data System (ADS)
Since micro- and nanostructures for photon management are of increasing importance in novel high-efficiency solar cell concepts, structuring techniques with up-scaling potential play a key role in their realization. Interference lithography and nanoimprint processes are presented as technologies for origination and replication of fine-tailored photonic structures on large areas. At first, these structure origination and replication technologies are presented in detail: With the interference pattern of two or more coherent waves, a wide variety of structures with feature sizes ranging from 100 nm to 100 ?m can be generated in photoresist by interference lithography. Examples are linear gratings, crossed gratings, hexagonal structures, three dimensional photonic crystals or surface-relief diffusers. The strength of this technology is that homogeneous structures can be originated on areas of up to 1.2 x 1.2 m2. The structures in photoresist, the so-called master structures, can serve as an etching mask for a pattern transfer, as a template for infiltration with different materials or they can be replicated via electroplating and subsequent replication processes. Especially in combination with replication steps, the industrially feasible production of elaborate structures is possible. As a particularly interesting process, nanoimprint lithography (NIL) is described in detail. As a way towards industrial production, a roller NIL tool is presented. After the description of the basic technologies, three application examples for solar cells are presented with details about the design of the structures, the structuring processes, sample characterization and evaluation: (1) honeycomb structures for the front side texturization of multicrystalline silicon wafer solar cells, (2) diffractive rear side gratings for absorption enhancement in the spectral region near the band gap of silicon, and (3) plasmonic metal nanoparticle arrays manufactured by combined imprint and lift off processes.
Bl�si, Benedikt; Hauser, Hubert; Walk, Christian; Michl, Bernhard; Guttowski, Aron; Mellor, Alexander; Benick, Jan; Peters, Marius; J�chter, Sabrina; Wellens, Christine; K�bler, Volker; Hermle, Martin; Wolf, Andreas J.
Hybrid Inorganic-Organic Heterojunction Solar Cell
NASA Astrophysics Data System (ADS)
In this study, solar cells were fabricated by spin-coating polyaniline (PANI) base (EB) over an n-type Si substrate. The final heterojunction's device structure was Al/ n-type Si/EB/Au. The electrical properties of the resultant device were investigated by measuring the current density-voltage ( J- V), capacitance-voltage ( C- V), and impedance characteristics in the dark and under illumination. N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and tetrahydrofuran (THF) were used as solvents for EB. The effects of these solvents on the photovoltaic cell parameters were investigated, and the open-circuit voltage ( V oc), short-circuit current density ( J sc), fill factor (FF), and energy conversion efficiency ( ?) were determined. It was found that heterojunctions fabricated using EB dissolved in NMP, DMF, and THF produced J sc of 10 mA/cm2, 5.123 mA/cm2, and 2.78 mA/cm2, respectively. Rollover and crossover phenomena in the J- V curves under illumination were explained based on the back-contact barrier and surface recombination of electrons at the back contact. The linearity of Mott-Schottky plots indicated the formation of a heterojunction between EB and n-type Si, and the slope of 1/ C 2 versus voltage changed under illumination. The high values of shunt resistance were decreased under illumination, indicating that the efficiency of this type of heterojunction solar cell was limited by shunt resistance and the narrow absorption range of the solar spectrum by EB.
Ebrahim, Shaker; Soliman, Moataz; Abdel-Fattah, Tarek M.
Studies of encapsulant materials for terrestrial solar-cell arrays
NASA Technical Reports Server (NTRS)
Study 1 of this contract is entitled ""Evaluation of World Experience and Properties of Materials for Encapsulation of Terrestrial Solar-Cell Arrays.'' The approach of this study is to review and analyze world experience and to compile data on properties of encapsulants for photovoltaic cells and for related applications. The objective of the effort is to recommend candidate materials and processes for encapsulating terrestrial photovoltaic arrays at low cost for a service life greater than 20 years. The objectives of Study 2, ""Definition of Encapsulant Service Environments and Test Conditions,'' are to develop the climatic/environmental data required to define the frequency and duration of detrimental environmental conditions in a 20-year array lifetime and to develop a corresponding test schedule for encapsulant systems.
Carmichael, D. C. (compiler)
Development of flight ready fifty-micron-thick silicon solar cell array module technology
NASA Technical Reports Server (NTRS)
The development of ultrathin silicon solar cell array modules from initial design to flight testing is discussed. Three 80-cell modules were subjected to the thermal soak test, the LEO thermal cycle test, and the solar array flight experiment, and six 48-cell welded modules were evaluated in the geosynchronous orbit thermal cycle test. It is observed that the electrical performance of the modules was not affected by the different environmental conditions. The automatic assembly of the cell modules, in particular the welding and solar cell glassing operation, is described. The specific power capabilities of Kapton, Kapton-Kevlar-Kapton, Kapton-graphite-Kapton, and Kapton-graphite-aluminum honeycomb-graphite solar array designs are assessed.
Patterson, R. E.; Mesch, H. G.; Scott-Monck, J.
Laser-assisted solar cell metallization processing
NASA Technical Reports Server (NTRS)
Laser-assisted processing techniques utilized to produce the fine line, thin metal grid structures that are required to fabricate high efficiency solar cells are examined. Two basic techniques for metal deposition are investigated; (1) photochemical decomposition of liquid or gas phase organometallic compounds utilizing either a focused, CW ultraviolet laser (System 1) or a mask and ultraviolet flood illumination, such as that provided by a repetitively pulsed, defocused excimer laser (System 2), for pattern definition, and (2) thermal deposition of metals from organometallic solutions or vapors utilizing a focused, CW laser beam as a local heat source to draw the metallization pattern.
Dutta, S.
Transmutation doping of silicon solar cells
NASA Technical Reports Server (NTRS)
Normal isotopic silicon contains 3.05% of Si-30 which transmutes to P-31 after thermal neutron absorption, with a half-life of 2.6 hours. This reaction is used to introduce extremely uniform concentrations of phosphorus into silicon, thus eliminating the areal and spatial inhomogeneities characteristic of chemical doping. Annealing of the lattice damage in the irradiated silicon does not alter the uniformity of dopant distribution. Transmutation doping also makes it possible to introduce phosphorus into polycrystalline silicon without segregation of the dopant at the grain boundaries. The use of neutron transmutation doped (NTD) silicon in solar cell research and development is discussed.
Wood, R. F.; Westbrook, R. D.; Young, R. T.; Cleland, J. W.
Dip-coated sheet silicon solar cells
NASA Technical Reports Server (NTRS)
A cost-effective method is being developed for producing solar cell quality sheet silicon by dip coating inexpensive ceramic substrates with a thin layer of large grain silicon. Mullite (Aluminum Silicate) ceramic substrates coated with a thin layer of graphite have been dipped into molten silicon to produce 20-150 micron thick layers having grain sizes as large as .4 cm x 4 cm. With these silicon layers photovoltaic diodes have been fabricated with measured and inherent conversion efficiencies of 4% and 7%, respectively.
Heaps, J. D.; Maciolek, R. B.; Zook, J. D.; Scott, M. W.
Plastic solar cell interface and morphological characterization
NASA Astrophysics Data System (ADS)
Plastic solar cell research has become an intense field of study considering these devices may be lightweight, flexible and reduce the cost of photovoltaic devices. The active layer of plastic solar cells are a combination of two organic components which blend to form an internal morphology. Due to the poor electrical transport properties of the organic components it is important to understand how the morphology forms in order to engineer these materials for increased efficiency. The focus of this thesis is a detailed study of the interfaces between the plastic solar cell layers and the morphology of the active layer. The system studied in detail is a blend of P3HT and PCBM that acts as the primary absorber, which is the electron donor, and the electron acceptor, respectively. The key morphological findings are, while thermal annealing increases the crystallinity parallel to the substrate, the morphology is largely unchanged following annealing. The deposition and mixing conditions of the bulk heterojunction from solution control the starting morphology. The spin coating speed, concentration, solvent type, and solution mixing time are all critical variables in the formation of the bulk heterojunction. In addition, including the terminals or inorganic layers in the analysis is critical because the inorganic surface properties influence the morphology. Charge transfer in the device occurs at the material interfaces, and a highly resistive transparent conducting oxide layer limits device performance. It was discovered that the electron blocking layer between the transparent conducting oxide and the bulk heterojunction is compromised following annealing. The electron acceptor material can diffuse into this layer, a location which does not benefit device performance. Additionally, the back contact deposition is important since the organic material can be damaged by the thermal evaporation of Aluminum, typically used for plastic solar cells. Depositing a thin thermal and momentum blocking layer of lithium fluoride prevents damage which ultimately leads to higher efficiencies. Finally, new materials have been synthesized with better electronic properties and stability. Characterization of the polymer properties and how they assemble is important for high device performance. One new promising polymer, Polybenzo[1,2-b:4,5- b']dithiophene-4,7-dithien-2-yl-2,1,3-benzothiadiazole (PBnDT-DTBT), was characterized with PCBM and it was found that this polymer assembles similarly to previously studied polymers. The efficiency gained with this new polymer is obtained from an improvement in the materials electronic properties since the morphology closely resembles the P3HT:PCBM system.
Guralnick, Brett W.
Space environmental effect on solar cells: LDEF and other flight tests
NASA Technical Reports Server (NTRS)
This paper summarizes results of several experiments flown on the Long Duration Exposure Facility (LDEF) to examine the effects of the space environment on materials and technologies to be used in solar arrays. The various LDEF experiments are compared to each other as well as to other solar cell flight data published in the literature. Data on environmental effects such as atomic oxygen, ultraviolet light, micrometeoroids and debris, and charged particles are discussed in detail. The results from the LDEF experiments allow us to draw several conclusions. Atomic oxygen erodes unprotected silver interconnects, unprotected Kapton, and polymer cell covers, but certain dielectric coatings can protect both silver and Kapton. Cells that had wrap-around silver contacts sometimes showed erosion at the edges, but more recently developed wrap-through cells are not expected to have these problems. Micrometeoroid and debris damage is limited to the area close to the impact, and microsheet covers provide the cells with some protection. Damage from charged particles was as predicted, and the cell covers provided adequate protection. In general, silicon cells with microsheet covers showed very little degradation, and solar modules showed less than 3 percent degradation, except when mechanically damaged. The solar cell choices for the Space Station solar array are supported by the data from LDEF.
Gruenbaum, Peter; Dursch, Harry
LEO effects on candidate solar cell cover materials
NASA Technical Reports Server (NTRS)
In 1984, the LDEF (Long Duration Exposure Facility) was placed in LEO (Low Earth Orbit) for a mission planned to last approximately one year. Due to a number of factors, retrieval was delayed until 1990. An experiment, prepared under the direction of JPL, consisted of a test plate with thirty (30) individual thin silicon solar cell/cover samples. The covers consisted of conventional cerium doped microsheet platelets and potential candidate materials, such as FEP Teflon, silicon RTV's, glass resins, polyimides, and a silicone-polyimide copolymer encapsulant. The effects of the LDEF mission environment (micrometeorite/debris impacts, atomic oxygen, UV, and particulate radiation) on the samples are discussed.
Stella, Paul M.
Spray CVD for Making Solar-Cell Absorber Layers
NASA Technical Reports Server (NTRS)
Spray chemical vapor deposition (spray CVD) processes of a special type have been investigated for use in making CuInS2 absorber layers of thin-film solar photovoltaic cells from either of two subclasses of precursor compounds: [(PBu3) 2Cu(SEt)2In(SEt)2] or [(PPh3)2Cu(SEt)2 In(SEt)2]. The CuInS2 films produced in the experiments have been characterized by x-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and four-point-probe electrical tests.
Banger, Kulbinder K.; Harris, Jerry; Jin, Michael H.; Hepp, Aloysius
High efficiency thin-film GaAs solar cells
NASA Technical Reports Server (NTRS)
Several oxidation techniques are discussed which have been found to increase the open circuit (V sub oc) of metal-GaAs Schottky barrier solar cells, the oxide chemistry, attempts to measure surface state parameters, the evolving characteristics of the solar cell as background contamination (has been decreased, but not eliminated), results of focused Nd/YAG laser beam recrystallization of Ge films evaporated onto tungsten, and studies of AMOS solar cells fabricated on sliced polycrystalline GaAs wafers. Also discussed are projected materials availability and costs for GaAs thin-film solar cells.
Stirn, R. J.
Investigation of back surface fields effect on bifacial solar cells
NASA Astrophysics Data System (ADS)
A bifacial solar cell, in contrast with a conventional monofacial solar cell, produces photo-generated current from both front and back sides. Bifacial solar cell is an attractive candidate for enhancing photovoltaic (PV) market competitiveness as well as supporting the current efforts to increase efficiency and lower material costs. This paper reports on the fabrication of bifacial solar cells using phosphorus-oxytrichloride (POCl3) emitter formation on p-type, nanotextured silicon (Si) wafer. Backside surface field was formed through Al-diffusion using conventional screen-printing process. Bifacial solar cells with a structure of n+pp+ with and without back surface field (BSF) were fabricated in which silicon nitride (SiN) anti reflection and passivation films were coated on both sides, followed by screen printing of Argentum (Ag) and Argentum/Aluminum (Ag/Al) on front and back contacts, respectively. Bifacial solar cells without BSF exhibited open circuit voltage (VOC) of 535 mV for front and 480 mV for back surface. With Al-alloyed BSF bifacial solar cells, the VOC improved to 580 mV for the front surface and 560 mV for the back surface. Simulation of bifacial solar cells using PC1D and AFORS software demonstrated good agreement with experimental results. Simulations showed that best bifacial solar cells are achieved through a combination of high lifetime wafer, low recombination back surface field, reduced contact resistance, and superior surface passivation.
Sepeai, Suhaila; Sulaiman, M. Y.; Sopian, Kamaruzzaman; Zaidi, Saleem H.
Erroneous efficiency reports harm organic solar cell research
NASA Astrophysics Data System (ADS)
Mischaracterization of solar cell power conversion efficiencies and widespread publication of inconsistent data in scientific journals threatens to undermine progress in organic and hybrid photovoltaics research.
Zimmermann, Eugen; Ehrenreich, Philipp; Pfadler, Thomas; Dorman, James A.; Weickert, Jonas; Schmidt-Mende, Lukas
Current status of silicon solar cell technology
NASA Technical Reports Server (NTRS)
Recent advances in solar cell technology have led to the development of laboratory cells with efficiencies above 15% and production cells with efficiencies in the area of 13%. The increased output is largely the result of increases in the short-circuit current. The most significant gain in the amount of light entering the cell has been obtained through surface texturing by chemical etching techniques. Sheet resistances resulting from phosphorus diffusion in the 800 C temperature range yield junction depths on the order of 0.1 micrometer, leading to significant increases in the blue region of the cell spectral response. The inclusion of a back surface field in 10 ohm-cm cells has produced an increase in open-circuit voltage of about 50 mV and an increase in the minority carrier lifetime. It appears that a low emitter efficiency of the diffused region is the cause of poor voltages. Future research will be primarily directed toward correcting this deficiency and toward the development of low cost production methods.
Brandhorst, H. W., Jr.
Characterization testing of large area solar cell assemblies
A complete characterization program has been performed on two large area (7 cm x 6 cm) solar cell types which will be used on the Hughes HS 393 satellite solar arrays. Each type was subjected to a series of tests which provided the data needed to accurately predict the solar array performance at end of life and demonstrated the mechanical
Jay S. Fodor; Steven W. Gelb; Leland J. Goldhammer; George S. Goodelle; Audrey L. Judson
Questions I will answer What is a solar cell?
material. CdS/CdTe glass #12;20 CdTe: Industrial Status First Solar is the leader. It takes them 2.5 hours % $1.15/W Suntech, Sunpower CdTe 17.3 % 11 % $0.75/W First Solar Cd are solar cells made? · How do they work? · How efficient can they be? · How
McGehee, Michael
Recyclable organic solar cells on cellulose nanocrystal substrates
Solar energy is potentially the largest source of renewable energy at our disposal, but significant advances are required to make photovoltaic technologies economically viable and, from a life-cycle perspective, environmentally friendly, and consequently scalable. Cellulose nanomaterials are emerging high-value nanoparticles extracted from plants that are abundant, renewable, and sustainable. Here, we report on the first demonstration of efficient polymer solar cells fabricated on optically transparent cellulose nanocrystal (CNC) substrates. The solar cells fabricated on the CNC substrates display good rectification in the dark and reach a power conversion efficiency of 2.7%. In addition, we demonstrate that these solar cells can be easily separated and recycled into their major components using low-energy processes at room temperature, opening the door for a truly recyclable solar cell technology. Efficient and easily recyclable organic solar cells on CNC substrates are expected to be an attractive technology for sustainable, scalable, and environmentally-friendly energy production. PMID:23524333
Zhou, Yinhua; Fuentes-Hernandez, Canek; Khan, Talha M.; Liu, Jen-Chieh; Hsu, James; Shim, Jae Won; Dindar, Amir; Youngblood, Jeffrey P.; Moon, Robert J.; Kippelen, Bernard
Consciousness can reduce the voltage of the output signal of solar cell
NASA Astrophysics Data System (ADS)
When the sun's light radiate on the solar cell, the solar cell can produce the output signal as the photocurrent. We use the Data Acquisition Modules to record the voltage of the output signals. The v1 is voltage of the output signal of solar cell1; The v2 is the one of solar cell2. And these two solar cells stay side by side. When we record the voltage of the output signal from the morning to the noon, the voltage of the output signals will go up, and the v1 is bigger than the v2 during this time. But when the experimenter use consciousness to reduce the voltage of the output signals. That is to say: not only natural light ratiade on two solar cells, but also consciousness act on two solar cells. Not only I can use consciousness to reduce the growth voltage of the output signals, but also can change the v1 to be littler than the v2. The experiment was conducted on Sep. 2010. There is the physical system of the mass, energy, space and time-MEST; There is the spirited system of the mind, consciousness, emotion and desire-MECD; the information system is the code system. We can use them to develop photoelectric principle, life technology and Nanotech of semiconductor for consciousness effect.
Cao, Dayong
A three solar cell system based on a self-supporting, transparent AlGaAs top solar cell
NASA Technical Reports Server (NTRS)
Development of a three solar cell stack can lead to practical efficiencies greater than 30 percent (1x,AM0). A theoretical efficiency limitation of 43.7 percent at AM0 and one sun is predicted by this model. Including expected losses, a practical system efficiency of 36.8 percent is anticipated. These calculations are based on a 1.93eV/1.43eV/0.89eV energy band gap combination. AlGaAs/GaAs/GaInAsP materials can be used with a six-terminal wiring configuration. The key issues for multijunction solar cells are the top and middle solar cell performance and the sub-bandgap transparency. AstroPower has developed a technique to fabricate AlGaAs solar cells on rugged, self-supporting, transparent AlGaAs substrates. Top solar cell efficiencies greater than 11 percent AM0 have been achieved. State-of-the-art GaAs or InP devices will be used for the middle solar cell. GaInAsP will be used to fabricate the bottom solar cell. This material is lattice-matched to InP and offers a wide range of bandgaps for optimization of the three solar cell stack. Liquid phase epitaxy is being used to grow the quaternary material. Initial solar cells have shown open-circuit voltages of 462 mV for a bandgap of 0.92eV. Design rules for the multijunction three solar cell stack are discussed. The progress in the development of the self-supporting AlGaAs top solar cell and the GaInAsP bottom solar cell is presented.
Negley, Gerald H.; Rhoads, Sandra L.; Terranova, Nancy E.; Mcneely, James B.; Barnett, Allen M.
Next generation CIGS for solar cells
NASA Astrophysics Data System (ADS)
An overview is presented of the PV-ACIST project. The goal of this project is to demonstrate proof-of-concept of next generation CuIn1-xGax(SySe1-y)2 (CIGS)-based solar cells. The first phase of the project began with a theoretical analysis of the potential of tandem-junction devices. This analysis showed that efficiencies could exceed 25% based constituent junctions comparable to the best achieved in single CIGS junctions. Subsequent efforts have focused on development and characterization of the materials and processes necessary to achieve the wide-gap device portion of the tandem structure and on modeling of device results based on both wide and narrow gap materials. Results to date have included demonstration of wide gap devices, characterization of the diffusivity of Ga in CIGS under various process conditions, characterization and modeling of the conduction properties of ideal CIGS, and model results explaining the "red kink" effect in certain high-performance CIGS solar cells.
Rockett, A.; Birkmire, R.; Morel, D.; Fonash, S.; Hou, J.-Y.; Marudachalam, M.; D'Amico, J.; Panse, P.; Zafar, S.; Schroeder, D. J.
Effects of excitons on solar cells
NASA Astrophysics Data System (ADS)
We have studied the effects of excitons on the two key parameters of a Si solar cell: the dark-saturation current and short-circuit current. We have found that the effect of excitons on the dark-saturation current is very sensitive to the boundary condition for excess excitons at the edge of the depletion region. With the assumption of near equilibrium between the electrons and excitons, we find that the exciton effect is rather small, which is contrary to the conclusion of significant reduction in the dark-saturation current made in previous work with the assumption of no excess excitons at the edge [J. Appl. Phys. 79, 195 (1996)]. The results for the short-circuit current are very similar to the previous work. However, the analytical results for the carrier concentrations and the corresponding currents are now presented in a simple way in which the physical meaning of each individual term is elucidated or revealed. Furthermore, we have found, for practical purposes, very accurate approximate solutions for the carrier concentrations and corresponding currents. Our conclusion is that the major effect of excitons on the Si solar cell performance relies on whether the effective diffusion length (L1) of the coupled electron-exciton system is significantly greater than that of the electron itself (Le).
Zhang, Yong; Mascarenhas, Angelo; Deb, Satyen
Solar light induced opacity of MIND cells
NASA Astrophysics Data System (ADS)
Multi-interface novel devices (MIND) exhibit a dramatically low UV- and blue-spectrum photovoltaic (PV) performance. A paradox could even be observed, the better the electronic passivation the poorer the PV performance. The paradox appears under relatively low excitations in comparison with intense laser fluxes usually at its origin. The effect can be explained by solar light induced opacity, which reduces considerably or even totally the photon penetration into deeper layers, from which exclusively the photocarrier collection is possible. This opacity results from a feedback occasioned by the free-carrier absorption: better surface passivation, higher free-carrier density, stronger surface dead zone absorptance. The total energy of the incident short wavelength beam can be absorbed before a carrier collection limit buried in the emitter. This limit acts simultaneously on the electronic performance, blocking free-carriers, and on the optical performance, being at the origin of an enhancement of the surface absorptance. As a consequence, a thin surface zone dominates the optical functions of MIND cells through the free-carrier gas confined inside it. In this work we report specific effects concerning the solar-light induced opacity in MIND cells. The investigation allows modification of the free-carrier confinement using different device architectures. The main characterization methods were reflectivity and spectral response with a varying incident beam. The results prove the domination of the free-carrier optical functions on the MIND PV conversion.
Kuznicki, Zbigniew T.; Meyrueis, Patrick
Computational studies of quantum dot sensitized solar cells
NASA Astrophysics Data System (ADS)
This thesis presents a computational study of quantum dot (QD) sensitized solar cells. First part deals with the non-equilibrium many-body theory or non-equilibrium Green's function (NEGF) theory. In this approach I study electron dynamics in the quantum-dot sensitized solar cell subjected to time-dependent fields. NEGF theory, because it does not impose any conditions on a perturbation, is the fundamental one to describe ultrafast processes in small, strongly correlated systems and/or in strong fields. In this research I do not only perform analytical derivation, but also design and implement spectral numerical solution for the resulting complex system of partial integrodifferential equations. This numerical solution yielded an order of magnitude speedup over the methods used previously in the field. The forth chapter of this thesis deals with calculation of optical properties and the ground state configuration of Zn2SnO4 (ZTO). ZTO is used by experimentalists in UW to grow nanorods which are then sensitized by QDs. ZTO is a challenging material for computational analysis because of its inverse spinel structure; thus it has an immense number of configurations matching the X-ray diffraction experiments. I've applied a cluster expansion method and have found the ground state configuration and phase diagram for ZTO. Calculations of optical properties of ground state bulk ZTO were done with a recently developed DFT functional. The optical band gap obtained in these calculations matched the experimental value. The last chapter describes development of the general simulator for interdigitated array electrodes. The application of this simulation together with the experiments may lead to understanding of reaction parameters and mechanisms important for development of electrochemical solar cells.
Kolesov, Grigory
Data compression experiments with high resolution solar images
High resolution movies are a critical tool for solar physics but they generate enormous amounts of data. Data storage and transfers can be a major bottleneck for observations and analysis on the ground but it becomes especially acute for solar instruments on small spacecraft with limited telemetry and on board storage capabilities. Recently there has been a great deal of progress in data compression techniques, especially in the area of lossy' techniques for continuous-tone images. These have the potential of reducing the storage and telemetry requirements of images by a factor of 10 or more while maintaining adequate quality for visual display. We have experimented with lossless and lossy techniques for a variety of photospheric, chromosperic, and coronal images. Algorithms used include the baseline JPEG (Joint Photographics Expert Group), the EPIC (Efficient Pyramid Image Coder), and the HCOMPRESS method. We indeed find that images and movies can reproduced from data compressed by factors from 10 to 20 which are virtually indistinguishable from the original to the eye. However, a visually acceptable image may not be adequate for more detailed analysis of solar movies, such as tracking structures, of the combination of images to form magnetograms or dopplegrams. Hence we have also experimented with analyzing data with different levels of compression to establish guidelines on the amount of compression tolerable for various types of analysis that might be performed on solar movies.
Shine, R.A.; Majani, E.E.
Efficiency improvement of silicon nanostructure-based solar cells
NASA Astrophysics Data System (ADS)
Solar cells based on a high-efficiency silicon nanostructure (SNS) were developed using a two-step metal-assisted electroless etching (MAEE) technique, phosphorus silicate glass (PSG) doping and screen printing. This process was used to produce solar cells with a silver nitrate (AgNO3) etching solution in different concentrations. Compared to cells produced using the single MAEE technique, SNS-based solar cells produced with the two-step MAEE technique showed an increase in silicon surface coverage of ?181.1% and a decrease in reflectivity of ?144.3%. The performance of the SNS-based solar cells was found to be optimized (?11.86%) in an SNS with a length of ?300 nm, an aspect ratio of ?5, surface coverage of ?84.9% and a reflectivity of ?6.1%. The ?16.8% increase in power conversion efficiency (PCE) for the SNS-based solar cell indicates good potential for mass production.
Huang, Bohr-Ran; Yang, Ying-Kan; Yang, Wen-Luh
Laser beam apparatus and method for analyzing solar cells
A laser beam apparatus and method for analyzing, inter alia, the current versus voltage curve at the point of illumination on a solar cell and the open circuit voltage of a solar cell. The apparatus incorporates a lock-in amplifier, and a laser beam light chopper which permits the measurement of the AC current of the solar cell at an applied DC voltage at the position on the solar cell where the cell is illuminated and a feedback scheme which permits the direct scanning measurements of the open circuit voltage. The accuracy of the measurement is a function of the intensity and wavelength of the laser light with respect to the intensity and wavelength distribution of sunlight and the percentage the dark current is at the open circuit voltage to the short circuit current of the solar cell.
Staebler, David L. (Lawrenceville, NJ)
Development of a shingle-type solar cell module
NASA Technical Reports Server (NTRS)
The development of a solar cell module, which is suitable for use in place of shingles on the sloping roofs of residental or commercial buildings, is reported. The design consists of nineteen series-connected 53 mm diameter solar cells arranged in a closely packed hexagon configuration. The shingle solar cell module consists of two basic functional parts: an exposed rigid portion which contains the solar cell assembly, and a semi-flexible portion which is overlapped by the higher courses of the roof installation. Consideration is given to the semi-flexible substrate configuration and solar cell and module-to-module interconnectors. The results of an electrical performance analysis are given and it is noted that high specific power output can be attributed to the efficient packing of the circular cells within the hexagon shape. The shingle should function for at least 15 years, with a specific power output of 98 W/sq w.
Shepard, N. F., Jr.; Sanchez, L. E.
Solar energy from spinach and toothpaste: fabrication of a solar cell in schools
NASA Astrophysics Data System (ADS)
We will show how pupils can make a solar cell with spinach, toothpaste and a few other items found in any school laboratory. This device is called a Graetzel cell, and could trigger off a revolution in photovoltaic technology.
Siemsen, F.; Bunk, A.; Fischer, K.; Korneck, F.; Engel, H.; Roux, D.
Flexible solar cells based on cadmium sulfide and telluride
Output parameters and diode characteristics under illumination of flexible thin-film solar cells ITO/CdS/CdTe/Cu/Au formed on polyimide films by vacuum methods are studied. Using mathematical modeling of the effect of diode characteristics under illumination on the efficiency, the physicothechnical parameters of such structures are optimized. This made it possible to obtain laboratory samples of flexible solar cells based on cadmium sulfide and telluride with an efficiency of 11.4%. Solar modules with an efficiency of 4.5% based on the developed flexible solar cells are formed for the first time.
Khrypunov, G. S., E-mail: firstname.lastname@example.com; Chernykh, E. P.; Kovtun, N. A. [National Technical University 'Kharkov Polytehcnical Institute' (Ukraine); Belonogov, E. K. [Voronezh State Technical University (Russian Federation)], E-mail: firstname.lastname@example.com
Opportunities for Probing Fundamental Gravity with Solar System Experiments
The recent discovery of "dark energy" has challenged Einstein's general theory of relativity as a complete model for our macroscopic universe. From a theoretical view, the challenge is even stronger: general relativity clearly does not extend to the very small, where quantum mechanics holds sway. Fundamental physics models thus require some major revisions. We must explore deeper to both constrain and inspire this needed new physics. In the realm of the solar-system, we can effectively probe for small deviations from the predictions of general relativity: Technology now offers a wide range of opportunities to pursue experiments with accuracies orders of magnitude better than yet achieved. We describe both the relevant theoretical backgrounds and the opportunities for far more accurate solar system experiments.
Slava G. Turyshev; Thomas W. Murphy, Jr.; Eric G. Adelberger; James Battat; Douglas Currie; William M. Folkner; Jens Gundlach; Stephen M. Merkowitz; Kenneth L. Nordtvedt; Robert D. Reasenberg; Irwin I. Shapiro; Michael Shao; Christopher W. Stubbs; Massimo Tinto; James G. Williams; Nan Yu
Discrete mechanism damping effects in the solar array flight experiment
NASA Technical Reports Server (NTRS)
Accelerometer data were collected during on-orbit structural dynamic testing of the Solar Array Flight Experiment aboard the Space Shuttle, and were analyzed at Lockheed Missile and Space Co. to determine the amount of damping present in the structure. The results of this analysis indicated that the damping present in the fundamental in-plane mode of the structure substantially exceeded that of the fundamental out-of-plane mode. In an effort to determine the source of the higher in-plane damping, a test was performed involving a small device known as a constant-force spring motor or constant-torque mechanism. Results from this test indicate that this discrete device is at least partially responsible for the increased in-plane modal damping of the Solar Array Flight Experiment structure.
Pinson, E. D.
Production ready 30% efficient triple junction space solar cells
Spectrolab presents its next production GaInP\\/GaAs\\/Ge space triple junction solar cell, the XTJ space solar cell, averaging 29.8% efficiency at maximum power (AM0, 28�C, 135.3 mW\\/cm2) at beginning-of-life (BOL) testing of large populations (845 cells) of large-area solar cells without coverglass. Bare cells from this population with area of 26.62 cm2 have been tested to a maximum efficiency of 31.1%
Chris Fetzer; Bongim Jun; Kenneth Edmondson; Scott Khemthong; Kaveh Rouhani; Robert Cravens; Rina Bardfield; Mark Gillanders
Surface Magnetism: Relativistic Effects at Semiconductor Interfaces and Solar Cells
and a wedding-out and consolidation process seems to be unavoidable. One way out is the production of highly efficient solar cells by minimal costs. So far, however, such an optimization of the cells is mainly based
Schmidt, Wolf Gero
Simulated space environment tests on cadmium sulfide solar cells
NASA Technical Reports Server (NTRS)
Cadmium sulfide (Cu2s - CdS) solar cells were tested under simulated space environmental conditions. Some cells were thermally cycled with illumination from a Xenon-arc solar simulator. A cycle was one hour of illumination followed immediately with one-half hour of darkness. In the light, the cells reached an equilibrium temperature of 60 C (333 K) and in the dark the cell temperature dropped to -120 C (153 K). Other cells were constantly illuminated with a Xenon-arc solar simulator. The equilibrium temperature of these cells was 55 C (328 K). The black vacuum chamber walls were cooled with liquid nitrogen to simulate a space heat sink. Chamber pressure was maintained at 0.000001 torr or less. Almost all of the solar cells tested degraded in power when exposed to a simulated space environment of either thermal cycling or constant illumination. The cells tested the longest were exposed to 10.050 thermal cycles.
Clarke, D. R.; Oman, H.
Recent developments in evaporated CdTe solar cells
Recent developments in the technology of high vacuum evaporated CdTe solar cells are reviewed. High-efficiency solar cells of efficiencies up to 12.5% have been developed on soda-lime glass substrates with a low-temperature (<450�C) process. This simple process is suitable for in-line production of large-area solar modules on glass as well as on flexible polymer films with a roll-to-roll deposition process.
G. Khrypunov; A. Romeo; F. Kurdesau; D. L. B�tzner; H. Zogg; A. N. Tiwari
Annealing characteristics of irradiated hydrogenated amorphous silicon solar cells
NASA Technical Reports Server (NTRS)
It was shown that 1 MeV proton irradiation with fluences of 1.25E14 and 1.25E15/sq cm reduces the normalized I(sub SC) of a-Si:H solar cell. Solar cells recently fabricated showed superior radiation tolerance compared with cells fabricated four years ago; the improvement is probably due to the fact that the new cells are thinner and fabricated from improved materials. Room temperature annealing was observed for the first time in both new and old cells. New cells anneal at a faster rate than old cells for the same fluence. From the annealing work it is apparent that there are at least two types of defects and/or annealing mechanisms. One cell had improved I-V characteristics following irradiation as compared to the virgin cell. The work shows that the photothermal deflection spectroscopy (PDS) and annealing measurements may be used to predict the qualitative behavior of a-Si:H solar cells. It was anticipated that the modeling work will quantitatively link thin film measurements with solar cell properties. Quantitative predictions of the operation of a-Si:H solar cells in a space environment will require a knowledge of the defect creation mechanisms, defect structures, role of defects on degradation, and defect passivation and annealing mechanisms. The engineering data and knowledge base for justifying space flight testing of a-Si:H alloy based solar cells is being developed.
Payson, J. S.; Abdulaziz, S.; Li, Y.; Woodyard, J. R.
Solar System experiments do not yet veto modified gravity models
The dynamical equivalence between modified and scalar-tensor gravity theories is revisited and it is concluded that it breaks down in the limit to general relativity. A gauge-independent analysis of cosmological perturbations in both classes of theories lends independent support to this conclusion. As a consequence, the PPN formalism of scalar-tensor gravity and Solar System experiments do not veto modified gravity, as previously thought.
Valerio Faraoni
Some observations of heated gallium arsenide heteroface solar cells
NASA Technical Reports Server (NTRS)
GaAlAs/GaAs heteroface solar cells used in space offer advantages of higher operating temperatures and recovery from radiation damage using thermal annealing. Experiments were conducted to examine the effects on the room temperature photovoltaic properties of cells due to heating in a vacuum at temperatures encountered in radiation damage annealing. Some degradation of photovoltaic properties was observed for all the cells that were heated. The lifetime, due to heating, for a 20-percent degradation in output power was estimated for cells heated at 200 C and 400 C. The results for cells that were heated at 200 C for 1750 hours indicate a lifetime of at least 3 years. The results for cells that were heated at 400 C for 264 hours indicate that lifetimes in the range of 350 hours to 1400 hours may be expected. The results indicate that for cells that must be heated at 400 C the selection of fabrication techniques and materials is particularly important.
Friesen, W. J.
CRADA Final Report: Process development for hybrid solar cells
TCF funding of a CRADA between LBNL and RSLE leveraged RSLE's original $1M investment in LBNL research and led to development of a solar cell fabrication process that will bring the high efficiency, high voltage hybrid tandem solar cell closer to commercialization. RSLE has already built a pilot line at its Phoenix, Arizona site.
Ager, Joel W
III-nitride compound semiconductors for solar cell
Solar cells are one of the best alternatives compared to our conventional or fossil energy and, thus, can play an important role in energy economy in an environment friendly fashion in the coming years. The main barrier of this technology is its low efficiency. Though the maximum theoretical efficiency of a solar cell teaches up to 86% but the practical
M. O. Islam; M. R. Islam; D. A. Jahan; A. A. M. Monzur-Ul-Akhir; Z. H. Mahmood
Analytical determination of critical crack size in solar cells
NASA Technical Reports Server (NTRS)
Although solar cells usually have chips and cracks, no material specifications concerning the allowable crack size on solar cells are available for quality assurance and engineering design usage. Any material specifications that the cell manufacturers use were developed for cosmetic reasons that have no technical basis. Therefore, the Applied Solar Energy Corporation (ASEC) has sponsored a continuing program for the fracture mechanics evaluation of GaAs. Fracture mechanics concepts were utilized to develop an analytical model that can predict the critical crack size of solar cells. This model indicates that the edge cracks of a solar cell are more critical than its surface cracks. In addition, the model suggests that the material specifications on the allowable crack size used for Si solar cells should not be applied to GaAs solar cells. The analytical model was applied to Si and GaAs solar cells, but it would also be applicable to the semiconductor wafers of other materials, such as a GaAs thin film on a Ge substrate, using appropriate input data.
Chen, C. P.
Solar cell nanotechnology for improved efficiency and radiation hardness
Space electronic equipment, and NASA future exploration missions in particular, require improvements in solar cell efficiency and radiation hardness. Novel nano-engineered materials and quantum-dot array based photovoltaic devices promise to deliver more efficient, lightweight solar cells and arrays which will be of high value to long term space missions. In this paper, we describe issues related to the development of
Alexander I. Fedoseyev; Marek Turowski; Qinghui Shao; Alexander A. Balandin
Silicon-fiber blanket solar-cell array concept
NASA Technical Reports Server (NTRS)
Proposed economical manufacture of solar-cell arrays involves parallel, planar weaving of filaments made of doped silicon fibers with diffused radial junction. Each filament is a solar cell connected either in series or parallel with others to form a blanket of deposited grids or attached electrode wire mesh screens.
Eliason, J. T.
Study of internal stresses of thin solar cell modules