Title: A Design Based on Stair-case Band Alignment of Electron Transport Layer for Improving Performance and Stability in Planar Perovskite Solar Cells,
Abstract: Among the n-type metal oxide materials used in the planar perovskite solar
cells, zinc oxide (ZnO) is a promising candidate to replace titanium dioxide
(TiO2) due to its relatively high electron mobility, high transparency, and
versatile nanostructures. Here, we present the application of low temperature
solution processed ZnO/Al-doped ZnO (AZO) bilayer thin film as electron
transport layers (ETLs) in the inverted perovskite solar cells, which provide a
stair-case band profile. Experimental results revealed that the power
conversion efficiency (PCE) of perovskite solar cells were significantly
increased from 12.25 to 16.07% by employing the AZO thin film as the buffer
layer. Meanwhile, the short-circuit current density (Jsc), open-circuit voltage
(Voc), and fill factor (FF) were improved to 20.58 mA/cm2, 1.09V, and 71.6%,
respectively. The enhancement in performance is attributed to the modified
interface in ETL with stair-case band alignment of ZnO/AZO/CH3NH3PbI3, which
allows more efficient extraction of photogenerated electrons in the CH3NH3PbI3
active layer. Thus, it is demonstrated that the ZnO/AZO bilayer ETLs would
benefit the electron extraction and contribute in enhancing the performance of
perovskite solar cells.