Supporting Information

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1 Supporting Information Synergistic Effect of Fluorine Substitution and Thio-Alkylation on Photovoltaic Performances of Alternating Conjugated Polymers Based on Alkylthio Substituted Benzothiadiazole-Quaterthiophene Ruipeng Peng, Huan Guo, Jingbo Xiao, Guo Wang, Songting Tan, * Bin Zhao, * Xia Guo * and Yongfang Li Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan , China * tanst2008@163.com (S. T),xtuzb@163.com (B. Z). Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou , China. * guoxia@suda.edu.cn (X. G). S-1

2 EXPERIMENTAL Materials. 4,7-Dibromobenzo[c][1,2,5]thiadiazole (6), 4,7-dibromo-5- fluorobenzo[c][1,2,5]thiadiazole (7), 4,7-dibromo-5,6-Difluorobenzo[c][1,2,5] thiadiazole (8), and (3,3'-difluoro-[2,2'-bithiophene]-5,5'-diyl)bis(trimethylstannane) (M4) were purchased from SunaTech Inc. Tetrahydrofuran (THF) and diethyl ether were refluxed over sodium and benzophenone, and distilled prior to use. All the other chemicals were purchased from commercial suppliers (Aldrich, Alfa, etc.) and used as received unless noted otherwise. Column chromatography was carried out on silica gel (Qingdao Banke Separation Materials Co, LTO, mesh). Instruments. 1 H NMR and 13 C NMR spectra were recorded on a Bruker AVANCE 400 spectrometer. Molecular mass was determined by matrix assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) using a BrukerAupoflex-III mass spectrometer. Thermal gravimetic analysis (TGA) was carried out on a SDT Q600 analyzer. Ultraviolet-Visible (UV-Vis) spectra were measured with a CARY 100 UV-Vis spectrometer. Cyclic voltammetry (CV) experiments were performed on an electrochemistry workstasion (ZAHNER ZENNIUM) with the polymer film on Pt slice as the working electrode, Pt slice as the counter electrode, and Ag/AgCl (saturated KCl) electrode as the reference electrode. The atomic microscopy (AFM) measurements were carried out on a Digital Instruments Enviro Scope instrument in the tapping mode. Transmission electron microscopy (TEM) were performed on a JEM-2100 electron microscope operating at an acceleration voltage of 100 kv. Device Fabrication and Characterization. The PSCs devices were fabricated with the structure of ITO/PEDOT:PSS/polymer:PC 71 BM/PFN-Br/Al. The ITO-coated glass substrates were cleaned with deionized water, acetone, and isopropanol, respectively. Subsequently, the pre-cleaned ITO-coated glass substrate was treated by UV-ozone for 20 min. PEDOT:PSS (Clecios P VP AI 4083, H.C.Starck) solution was spin-coated onto the pre-cleaned ITO coated glass substrates, and thermal-treated at S-2

3 150 C for 15 min. The active layer was then deposited on the top of the PEDOT:PSS layer by spin-coating from CB:σ-DCB solution (10 mg/ml of polymers) of polymer:pc 71 BM. In the case of the devices using a processing additive, CN (2.5% by volume) was added to the solution before use. The methanol solution of PFN-Br at a concentration of 0.5 mg/ml was deposited on the active layer at 3000 rpm for 30s. The thickness of the active layers was controlled by adjusting the spin speed during the spin-coating process and measured by a KLA Tencor D-100 profilometer. Finally, 100 nm of Al was successively deposited on the photosensitive layer under vacuum at a pressure of ca Pa. The overlapping area between the cathode and anode defined a pixel size of 0.04 cm 2. Except for the deposition of the PEDOT:PSS layers, all the fabrication processes were carried out inside a controlled atmosphere of nitrogen drybox containing less than 5 ppm oxygen and moisture. The PCE values of the PSCs were measured under an illumination of AM 1.5G (100 mw/cm 2 ) using a SS-F5-3A solar simulator (AAA grade, mm 2 photobeam size) of Enli Technology CO., Ltd. A monocrystalline silicon reference cell (SRC-00019) was purchased from Enli Technology CO., Ltd.. PCE statistics were obtained using 30 individual devices fabricated under the same conditions. The EQE was measured by a solar cell spectral response measurement system QE-R3011 of Enli Technology CO., Ltd. The light intensity at each wavelength was calibrated with a standard single crystal Si photovoltaic cell. SYNTHESIS 3-Mercapto-thiophene (1). A solution of 3-bromothiophene (8 g, 49.4 mmol) in dry diethyl ether (50 ml) was added at -70 C to a 2.5 M solution of n-butyl lithium in THF (20 ml, 49.4 mmol) under a nitrogen atmosphere and the mixture was stirred for 2 h at -70 C. To the solution was added dry sublimed sulfur (1.6 g, 49.4 mmol) and stirred at -70 o C for 2 h before quenching with 100 ml of water. The resulting mixture was extracted with NaOH (25 ml,1 M) three times. The combined aqueous layers were cooled with ice and acidified with 10 % hydrochloric acid to liberate the thiol from its sodium salt. The product was extracted with diethyl ether (3 50 ml). The S-3

4 organic layers were dried over anhydrous MgSO 4 and the solvent was removed by rotary evaporation. Clear yellow oil (5 g, 87 %). 3-((2-Octyldodecyl)thio)thiophene(2). A solution of potassium tert-butoxide (7.2 g, 64.5 mmol ) in anhydrous ethanol (40 ml) was added at 0 C to 3-mercapto-thiophene (5.0 g, 43.0 mmol) under a nitrogen atmosphere and mixture was stirred for 30 min at 0 C. 1-Bromo-2-octyldodecane (15.6 g, 43.2 mmol) was slowly added to the solution and the mixture was refluxed for 2 h before quenching with 100 ml of water. The product was extracted with diethyl ether (3 50 ml). The combined organic layers were dried over anhydrous MgSO 4 and the solvent was removed by rotary evaporation. The residue was isolated by silica gel column with petroleum ether to give colorless oil (15.4 g, 90 %). 1 H NMR (400 MHz, CDCl 3, TMS/ppm): δ 7.31 (d, J = 2.3 Hz, 1H), δ 7.07 (s, 1H), δ 7.00 (d, J = 4.7 Hz, 1H), δ 2.83 (d, J = 6.0 Hz, 2H), δ (m, 1H), δ (m, 32H), δ (m, 6H). 2-Bromo-3-((2-octyldodecyl)thio)thiophene(3). To a solution compound 2 (15 g, 37.9 mmol) in CHCl 2 (30 ml), a solution of NBS (6.7 g, 37.9 mmol) in DMF (10 ml) was added dropwise at 0 C. The reaction mixture was warmed to r.t. and stirred overnight. After washed with water, the organic layer was dried over anhydrous MgSO 4 and the solvent was evaporated. The residue was purified with silica gel column with petroleum ether to give colorless oil (17.6 g, 98 %). 1 H NMR (400 MHz, CDCl 3, TMS/ppm): δ 7.25 (d, 1H), δ 6.93 (d, 1H), δ 2.83 (d, 2H), δ (m, 1H), δ (m, 32H), δ (m, 6H). 2-Bromo-4-((2-octyldodecyl)thio)thiophene (4). A solution of lithium di-isopropylamide (15.8 ml, 31.7 mmol) in THF was added rapidly (5 min) to a solution of compound 3 (15 g, 31.7 mmol) in 30 ml dry THF at -70 C. The mixture was stirred at -70 C for 1 h. Then, The rearranged material was quenched with 0.1 M HCl, poured into water, and extracted with ether. The ether layer was dried over anhydrous MgSO 4 and the solvent was evaporated. The residue was purified with silica gel column with petroleum ether to give colorless oil (7.5 g, 50 %). 1 H NMR (400 MHz, S-4

5 CDCl 3, TMS/ppm): δ 6.98 (d, 1H), δ 6.96 (d, 1H), δ 2.81 (d, 2H), δ (m, 1H), δ (m, 32H), δ (m, 6H). Tributyl(4-((2-octyldodecyl)thio)thiophen-2-yl)stannane (5). A solution of n-butyl lithium (5.9 ml, 14.8 mmol) in THF was added dropwise to a solution of compound 4 (7 g, 14.8 mmol) in 20 ml dry THF at -78 C. The mixture was stirred at -78 C for 2 h. Then, tri-n-butyltin chloride (4 ml, 14.8 mmol) was added slowly. The solution was stirred at -70 C for additional 1 h, then allowed to warm to room temperature and stirred overnight. The product was extracted with CHCl 2. The combined organic layers were dried over anhydrous MgSO 4 and the solvent was removed by rotary evaporation. The crude product was directly used without further purification. Yellow oil (8.6 g, 85%). 4,7-Bis(4-((2-octyldodecyl)thio)thiophen-2-yl)benzo[c][1,2,5]thiadiazole(9). To a mixture of compound 5 (7.0 g, 10.2 mmol) and 4,7-dibromobenzo[c][1,2,5] thiadiazole (1 g, 3.4 mmol) in degassed toluene (30 ml), Pd(PPh 3 ) 4 (200 mg) was added and then refluxed for 48 h under nitrogen atmosphere. After cooling to room temperature, the product was extracted with CHCl 2. The combined organic layers were dried over anhydrous MgSO 4 and the solvent was removed by rotary evaporation. The residue was purified with silica gel column with petroleum ether/ch 2 Cl 2 (10:1) to dark red viscous liquid (1.9 g, 60%). 1 H NMR (400 MHz, CDCl 3, TMS/ppm): δ 8.05 (d, J = 1.2 Hz, 2H), δ 7.83(s, 2H), δ 7.19 (d, J = 1.27 Hz, 2H), δ 2.92 (d, J = 6.2 Hz, 4H), δ (m, 2H), δ (m, 64H), δ (m, 12H). MALDI-TOF MS (C 54 H 88 N 2 S 5 ) m/z: calcd for ; Found, Fluoro-4,7-bis(4-((2-octyldodecyl)thio)thiophen-2-yl)benzo[c][1,2,5]thiadia -zole (10). To a mixture of compound 5 (6.6 g, 9.6 mmol) and 4,7-dibromo-5-fluorobenzo[c] [1,2,5]thiadiazole (1 g, 3.2 mmol) in degassed toluene (30 ml), Pd(PPh 3 ) 4 (200 mg) was added and then refluxed for 48 h under nitrogen atmosphere. After cooling to room temperature, the product was extracted with CHCl 2. The combined organic layers were dried over anhydrous MgSO 4 and the solvent was S-5

6 removed by rotary evaporation. The residue was purified with silica gel column with petroleum ether/ch 2 Cl 2 (10:1) to dark red viscous liquid (2.3 g, 75%). 1 H NMR (400 MHz, CDCl 3, TMS/ppm): δ 8.21 (s, 1H), δ 8.07 (s, 1H), δ 7.75 (d, J = 1.6 Hz, 1H), δ 7.31 (s, 1H), δ 7.23 (s, 1H), δ 2.93 (d, J = 6.0 Hz, 4H), δ (m, 2H), δ (m, 64H), δ (m, 12H). MALDI-TOF MS (C 54 H 87 FN 2 S 5 ) m/z: calcd for ; Found, ,6-Difluoro-4,7-bis(4-((2-octyldodecyl)thio)thiophen-2-yl)benzo[c][1,2,5] thiadiazole (11). To a mixture of compound 5 (6.3 g, 9.2 mmol) and 4,7-dibromo-5,6-difluoro benzo[c][1,2,5]thiadiazole (1 g, 3 mmol) in degassed toluene (30 ml), Pd(PPh 3 ) 4 (200 mg) was added and then refluxed for 48 h under nitrogen atmosphere. After cooling to room temperature, the product was extracted with CHCl 2. The combined organic layers were dried over anhydrous MgSO 4 and the solvent was removed by rotary evaporation. The residue was purified with silica gel column with petroleum ether/ch 2 Cl 2 (10:1) to dark red viscous liquid (2.3 g, 80%). 1 H NMR (400 MHz, CDCl 3, TMS/ppm): δ 8.23 (s, 2H), δ 7.34(s, 2H), δ 2.92 (d, J = 6.2 Hz, 4H), δ (m, 2H), δ (m, 64H), δ (m, 12H). MALDI-TOF MS (C 54 H 86 FN 2 S 5 ) m/z: calcd for ; Found, ,7-Bis(5-bromo-4-((2-octyldodecyl)thio)thiophen-2-yl)benzo[c][1,2,5]thiadia -zole(m1). To a solution of compound 6(1.5 g, 1.6 mmol) in CHCl 3 (20 ml) was added NBS (0.6 g, 3.6 mmol) in one portion at 0 C. The reaction mixture was warmed to r.t. and stirred 2 h. After washed with water, the organic layer was dried over anhydrous MgSO 4 and the solvent was evaporated. The residue was purified with silica gel column with petroleum ether/ch 2 Cl 2 (5:1) to dark red viscous liquid (1.6 g, 90%). 1 H NMR (400 MHz, CDCl 3, TMS/ppm): δ 7.91 (s, 2H), δ 7.76 (s, 2H), δ 2.93 (d, J = 6.1 Hz, 4H), δ (m, 2H), δ (m, 64H), δ (m, 12H). 13 C NMR (100 MHz, CDCl 3, TMS/ppm): δ , , , , , , , 77.28, 77.02, 76.77, 40.05, 38.06, 33.00, 31.93, 31.92, 29.95, 29.69, 29.66, 29.65, 29.36, 26.61, 22.70, 22.69, MALDI-TOF MS (C 54 H 86 Br 2 N 2 S 5 ) m/z: calcd for ; Found, S-6

7 4,7-Bis(5-bromo-4-((2-octyldodecyl)thio)thiophen-2-yl)-5-fluorobenzo[c][1,2, 5] thiadiazole (M2). To a solution of compound 6(1.5 g, 1.6 mmol) in CHCl 3 (20 ml) was added NBS (0.6 g, 3.5 mmol) in one portion at 0 C. The reaction mixture was warmed to r.t. and stirred 2 h. After washed with water, the organic layer was dried over anhydrous MgSO 4 and the solvent was evaporated. The residue was purified with silica gel column with petroleum ether/ch 2 Cl 2 (5:1) to dark red viscous liquid (1.6 g, 90 %). 1 H NMR (400 MHz, CDCl 3, TMS/ppm): δ 8.12 (s, 1H), δ 7.90 (s, 1H), δ 7.68 (d, J = 12.8 Hz, 1H), δ (m, 4H), δ (m, 2H), δ (m, 64H), δ (m, 12H). 13 C NMR (100 MHz, CDCl 3, TMS/ppm): δ , , , , , , , , , , , , , 77.37, 77.05, 76.73, 40.01, 38.03, 33.00, 31.96, 29.73, 26.64, 22.73, MALDI-TOF MS (C 54 H 85 Br 2 N 2 S 5 ) m/z: calcd for ; Found, ,7-Bis(5-bromo-4-((2-octyldodecyl)thio)thiophen-2-yl)-5,6-difluorobenzo[c] [1,2,5]thiadiazole (M3). To a solution of compound 6(1.5 g, 1.6 mmol) in CHCl 3 (20 ml) was added NBS (0.6 g, 3.4 mmol) in one portion at 0 C. The reaction mixture was warmed to r.t. and stirred 2 h. After washed with water, the organic layer was dried over anhydrous MgSO 4 and the solvent was evaporated. The residue was purified with silica gel column with petroleum ether/ch 2 Cl 2 (5:1) to dark red viscous liquid (1.6 g, 90%). 1 H NMR (400 MHz, CDCl 3, TMS/ppm): δ 8.08 (s, 2H), δ 2.92 (d, J = 6.1 Hz, 4H), δ (m, 2H), δ (m, 64H), δ (m, 12H). 13 C NMR (100 MHz, CDCl 3, TMS/ppm): δ , , , , ,118.51, , 77.27, 77.22, 77.02, 76.77, 40.05, 38.05, 32.99, 31.93, 31.91, 29.94, 29.69, 29.67, 29.63, 29.37, 29.35, 26.59, 22.70, 22.68, MALDI-TOF MS (C 54 H 84 Br 2 N 2 S 5 ) m/z: calcd for ; Found, Polymerization for PSDTBT-DFDT. In an atmosphere of nitrogen, M1 (201 mg, 0.18 mmol) and M4 (99 mg, 0.18 mmol) were added into a two-neck flask. Next, 3 ml of chlorobenzene was added into the mixture. The reaction mixture was subjected to three freeze-pump-thaw cycles degassing process in order to remove O 2. Finally, Pd 2 (dba) 3 (3 mg) and P(o-tol) 3 (5 mg) were added to the reaction mixture and heated S-7

8 at 110 C for 72 h. The reaction mixture was cooled to room temperature and slowly added to methanol (200 ml). Then, precipitate was purified through continuous Soxhlet extractions with methanol, acetone, hexane, dichloromethane and chloroform. At last, the polymer was precipitated into methanol and collected via filtration and dried under high vacuum for 24 h. The dark green solid was obtained (143 mg, 68 %).M n = 60.7 Kg.mol 1, PDI = Polymerization for PSDTBT-DFDT. In an atmosphere of nitrogen, M2 (202 mg, 0.18 mmol) and M4 (98 mg, 0.18 mmol) were added into a two-neck flask. Next, 3 ml of chlorobenzene was added into the mixture. The reaction mixture was subjected to three freeze-pump-thaw cycles degassing process in order to remove O 2. Finally, Pd 2 (dba) 3 (3 mg) and P(o-tol) 3 (5 mg) were added to the added to the reaction mixture and heated at 110 C for 72 h. The reaction mixture was cooled to room temperature and slowly added to methanol (200 ml). Then, precipitate was purified through continuous Soxhlet extractions with methanol, acetone, hexane, dichloromethane and chloroform. At last, the polymer was precipitated into methanol and collected via filtration and dried under high vacuum for 24 h. The dark green solid was obtained (143 mg, 68 %). M n = 17.0 Kg.mol 1, PDI = Polymerization for PSDffTBT-DFDT. In an atmosphere of nitrogen, M3 (191 mg, 0.17 mmol) and M4 (91 mg, 0.17 mmol) were added into a two-neck flask. Next, 3 ml of chlorobenzene was added into the mixture. The reaction mixture was subjected to three freeze-pump-thaw cycles degassing process in order to remove O 2. Finally, Pd 2 (dba) 3 (3 mg) and P(o-tol) 3 (4 mg) were added to the added to the reaction mixture and heated at 110 C for 72 h. The reaction mixture was cooled to room temperature and slowly added to methanol (200 ml). Then, precipitate was purified through continuous Soxhlet extractions with methanol, acetone, hexane, dichloromethane and chloroform. At last, the polymer was precipitated into methanol and collected via filtration and dried under high vacuum for 24 h. The dark green solid was obtained (123 mg, 72 %). M n = 14.9 Kg.mol 1, PDI = S-8

9 Scheme S1. Synthetic routes of three polymers. (a) n-buli, S 8, Et 2 O; (b) (CH 3 ) 3 COK, RBr, EtOH; (c) NBS, CHCl 3 ; (d) LDA, 10 % HCI, THF; (e) n-buli, tri(n-butyl)tin chloride, THF; (f) 4,7-dibromobenzo[c][1,2,5]thiadiazole (6), 4,7-dibromo-5-fluorobenzo[c][1,2,5]thiadiazole (7), or 4,7-dibromo-5,6-difluorobenzo[c][1,2,5]thiadiazole(8), Pd(PPh 3 ) 4, toluene; (g) NBS, CHCl 3 ; (h) Pd 2 (dba) 3, P(o-tol) 3, CB. Figure S1. 1 H NMR spectrum of compound 4 in CDCl 3. S-9

10 Figure S2. 1 H NMR spectrum of compound 10 in CDCl 3. Figure S3. 1 H NMR spectrum of M1 in CDCl 3. S-10

11 Figure S4. 13 C NMR spectrum of M1 in CDCl 3. Figure S5. MS-TOF spectrum of M1 with a matrix CCA. S-11

12 Figure S6. 1 H NMR spectrum of M2 in CDCl 3. Figure S7. 13 C NMR spectrum of M2 in CDCl 3. S-12

13 Figure S8. MS-TOF spectrum of M2 with a matrix CCA Figure S9. 1 H NMR spectrum of M3 in CDCl 3. S-13

14 Figure S C NMR spectrum of M3 in CDCl 3. Figure S11. MS-TOF spectrum of M3 with a matrix CCA. S-14

15 X-ray Diffraction (XRD) Analysis (100) PSDTBT-DFDT PSDTfBT-DFDT PSDTffBT-DFDT Intensity (200) θ(Degree) Figure S12. XRD curves of the polymer films. S-15