Characterization methods
1 H (400 MHz) and 13 C NMR (100 MHz) spectra were recorded on a Bruker Ascend 400 spectrometer.
Characterization methods
The NMR peaks of each compound were assigned with chemical shifts (δ: ppm) and spectral splitting patterns are designated as singlet (s), doublet (d), triplet (t), quartet (q), and multiplet (m). Microwave reactions were performed by a microwave initiator (Biotage). UV-visible (UV-vis) absorption spectra were obtained using an UV/vis spectrometer (Lambda 35, PerkinElmer) over the wavelength from 300 nm to 900 nm. The cyclicvoltammetry (CV) was performed using a CH instruments electrochemical analyzer to study electrochemical properties of the small molecules. Pt disk electrode was used as a working electrode and a platinum (Pt) wire as a counter electrode. A 0.1M deoxygenated tetrabutylammonium hexafluorophosphate (Bu 4 NPF 6 ) solution in dichloromethane was used as an electrolyte at a scan rate of 50mV/s. All potentials were performed versus Ag/AgCl reference electrode. The redox potential of ferrocene/ferrocenium (Fc/Fc+) was used to calibrate under the same conditions. The thermal properties were carried out by a thermogravimetric analysis (TGA, TA instruments Q50 thermal analysis). Atomic force microscopy (AFM) was measured by using an XE-100 (Park system) in a noncontact mode. Transmission electron microscopy (TEM) images were recorded on a FEI (Tecnai F20 G 2 ).
Characterization methods
TEM samples were prepared from spin coating the blend solution on ITO/PEDOT:PSS substrate, and then floating the film in water, followed by lifting on a carbon-coated square mesh copper grid. Fouriertransform infrared spectroscopy (FT-IR) spectra were recorded on a PerkinElmer Spectrum 100 FT-IR spectrometer. Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was performed with trans-2-[3-(4-tert-butylphenyl)-2-methyl- 143.7, 136.7, 135.9, 135.1, 124.8, 124.4, 123.3, 31.71, 30.30, 28.91, 22.72, 14.22, -8.10 .
4-Bromo-5-fluoro-7-(5′-hexyl-[2,2′-bithiophene]-5-yl)benzo[c][1,2,5]thiadiazole (4)
Compound (1) 159.5, 154.38, 154.30, 148.9, 146.8, 141.3, 135.1, 134.1, 129.9, 127.39, 127.29, 125.2, 124.4, 123.9, 115.49, 115.19, 95.95, 95.70, 31.70, 31.65, 30.37, 28.91, 22.71, 14 .22. 153.58, 151.22, 151.02, 150.36, 150.16, 149.99, 149.93, 147.76, 147.68, 147.56, 146.89, 142.20, 142.13, 134.0, 132.46, 132.36, 129.01, 125.2, 124.4, 123.2, 113.37, 113.25, 96.62, 96.40, 31.71, 31.64, 30.4, 28.9, 22.7, 14 .2. 145.8, 143.3, 140.1, 138.1, 134.3, 132.3, 36.16, 36.08, 35.87, 35.84, 29.12, 29.08, 23.15, 17.9, 14.31, 14.29, 10.98, -7 .99.
4-Bromo

4,4-

4-(4,4-Bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2-yl)-5-fluoro-7-(5′-hexyl-[2,2′-bithiophene]-5-yl)benzo[c][1,2,5]thiadiazole (9)
Compound (4) 6, 156.0, 152.14, 152.02, 150.77, 150.70, 148.5, 147.9, 145.2, 142.63, 142.57, 142.52, 141.8, 139.1, 134.8, 133.3, 132.33, 132.25, 132.14, 128.8, 127.8, 124.9, 123.88, 123.37, 123.26, 122.83, 122.58, 114.98, 114.66, 110.51, 110.36, 34.94, 34.91, 34.7, 34.68, 30.56, 30.45, 29.18, 27.95, 27.93, 27.86, 27.83, 27.79, 21.99, 21.97, 21.58, 16.77, 16.71, 16.63, 13.16, 13.13, 13.07, 9.80, 9 .77.
4-(6-Bromo-4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2-yl)-5-fluoro-7-(5′-hexyl-[2,2′-bithiophene]-5-yl)benzo[c][1,2,5]thiadiazole (10)
In a two-necked flasks under avoiding any light source, compound (9) (991 mg, 1.21 mmol) was dissolved in chloroform (92 mL). The solution was cooled to 0 °C in an ice bath and N-bromosuccinimide (NBS) (226.1 mg, 1.27 mmol) was added by small portions. After removing the ice bath, the reaction was stirred for 24 achavez@example.com.. After the reaction was completed, the mixture was extracted with chloroform and washed with brine and water. Organic phase was dried over anhydrous MgSO 4 and the solvent was evaporated under reduced pressure. The crude product then was purified by column chromatography using a hexane/CH 2 Cl 2 (19:1) to give a dark blue oil compound (10) 157.2, 153.0, 152.9, 151.10, 151.04, 149.52, 149.43, 146.2, 143.8, 141.9, 140.3, 135.8, 134.4, 134.08, 134.02, 133.05, 132.94, 132.5, 129.0, 124.9, 124.54, 124.44, 123.9, 123.6, 115.7, 115.4, 112.1, 111.23, 111.08, 36.06, 35.86, 31.72, 31.53, 30.3, 29.08, 29.0, 23.1, 22.7, 17.86, 17. 77, 17.68, 14.32, 14.22, 10.9 . Compound (10) 7, 157.2, 154.7, 153.3, 153.2, 152.0, 149.6, 146.3, 145.3, 143.06, 143.00, 142.90, 140.2, 139.5, 138.1, 136.1, 134.5, 133.62, 133.52, 133.40, 133.31, 128.96, 125.0, 124.38, 124.27, 123.94, 123.72, 116.11, 115.78, 111.79, 111.63, 36.17, 36.08, 35.88, 35.82, 31.73, 31.59, 30.3, 29.14, 29.08, 28.96, 23.2, 22.7, 17.99, 17.95, 14.34, 14.33, 14.23, 11.0, -8.0 . 
4-(4,4-

Synthesis of 0F

Synthesis of 1F
Compound (11) 2868, 2854, 1733, 1710, 1629, 1568, 1530, 1491, 1460, 1441, 1360, 1345, 1268, 1251, 1179, 1163, 1100, 1050, 965, 923, 879, 825, 794, 783, 753, 724, 613, 517, 495, 472, , 6.12; N, 4.66; S, 21.34; found C, 63.82; H, 6.08; N, 4.68; S, 21.30 .
Synthesis of 3F
Compound (11) 152.64, 152.58, 151.29, 151.22, 151.05, 150.84, 150.62, 150.55, 150.35, 149.68, 149.63, 148.75, 148.67, 148.5, 148.26, 148.0, 146.49, 146.47, 144.66, 144.31, 141.18, 141.12, 140.4, 136.04, 136.02, 134.72, 134.65, 134.15, 134.08, 134.03, 134.00, 133.31, 133.21, 133.07, 131.57, 131.49, 123.0, 129.1, 124.93, 124.85, 124.14, 124.10, 123.8, 123.2, 116.1, 115.8, 112.0, 111.9, 111.51, 111.35, 110.83, 110.79, 110.71, 36.04, 35.88, 31.31, 31.19, 30.0, 28.98, 28.54, 22.8, 22.3, 18.1, 13.80, 13.74, 10.67 .
Synthesis of 3F
IR (neat, v max /cm -1 ): 2954, 2918, 2869, 2850, 1725, 1707, 1629, 1574, 1489, 1463, 1439, 1365, 1340, 1246, 1177, 1102, 1050, 996, 965, 881, 814, 796, 785, 748, 724, 609, 518, 504, 476, 442 . , 5.78; N, 4.53; S, 20.72; found C, 62.16; H, 5.79; N, 4.684 S, 20.81 .
MALDI-TOF MS

Synthesis of 4F
Compound (12) 26, 152.20, 150.77, 150.42, 148.71, 148.62, 148.40, 148.18, 148.05, 146.50, 144.7, 141.31, 141.25, 141.18, 134.14, 134.05, 134.0, 133.9, 133.6, 133.56, 133.52, 131.62, 131.52, 129.99, 129.94, 129.92, 124.84, 124.13, 123.2, 111.86, 111.74, 110.97, 110.85, 36.04, 35.89, 31.31, 31.19, 30.05, 28.98, 28.55, 22.76, 22.29, 18.05, 13.79, 13.74, 10.7 .
Synthesis of 4F
IR (neat, v max /cm -1 ): 2954, 2921, 2968, 2852, 1723, 1707, 1655, 1629, 1574, 1561, 1532, 1517, 1487, 1463, 1441, 1421, 1355, 1342, 1242, 1177, 1096, 1045, 1000, 960, 884, 849, 814, 790, 750, 726, 611, 525, 518, 506, 474, 442 . H, 5.62; N, 4.46; S, 20.42; found C, 61.19; H, 5.58; N, 4.50 S, 20.48 .
MALDI-TOF MS

Theoretical calculation method
Density functional theory (DFT) calculations using Gaussian 09 at the B3LYP level with a 6-311G(d,p) basis set was carried out to determine the electronic and conformation properties of the molecules. The dipole moment was calculated from the optimized structure and its magnitude and direction were designated by an arrow from the center of a cross dashed line corresponding to the center of each molecule.
OTFT device fabrication and characterization
Bottom gate / top contact OTFTs were fabricated on a common gate of highly n-doped silicon with a 100- humidity. An HTM layer was prepared by 0F and 2F solution in toluene (60 mg/mL) . The HTM was formed by spin-coating at 2000 rpm for 30 s. Finally, a 60 nm-thick Au layer was formed by thermal evaporation to form the back contact. The active area was fixed to 0.16 cm 2 . All precursor preparation and device fabrication were carried out under air condition and humidity of about 35%.
Solar cell measurement
The devices were characterized by using a Keithley model 2400 source meter under AM1.5G at sun light intensity (100 mW/cm 2 ) in ambient air. A class-A solar simulator with a 1000 W Xenon lamp (Yamashita Denso) was used as a light source. Its light intensity was calibrated by using a NREL-calibrated Si solar cell coupled with KG-5 filter. External quantum efficiencies (EQE) were recorded on incident photon-tocurrent conversion equipment (Mcscience), calibrated by a G425 silicon photodiode. 

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