## 2 Experimental Section
### Polymers Synthesis  
**Synthesis of poly[4,4-dicotyl-2,6-dithien0[3,2-b2,3'-d]siloide-\(alt\)-5,5-(4,7'-bis(2-thienyl)-2',1',3'-benzothiadiazole-5,6-N-(3,7-dimethyloctyl)-dicarboxylic imide) (PDSTDBTDIDIDMO):** (89.0 mg, 0.134 mmol) of M1, (100.0 mg, 0.134 mmol) of M3, (2.2 mg, 0.0097 mmol) of Pd(OAc)\({}_{2}\) and (6.1 mg, 0.020 mmol) of P(o-tol)\({}_{3}\) were mixed and degassed under argon. Dry toluene (5 mL) was added and the system was further degassed and heated for 72 h at 110 \({}^{\circ}\)C. The reaction mixture was cooled to room temperature and dissolved in 300 mL CHCl\({}_{3}\). Ammonium hydroxide solution (50 mL) was then added to the mixture stirredovernight. The organic phase was subsequently separated and washed with deionized water. Later, the organic phase was reduced to about 50 mL and put into 300 mL methanol and stirred overnight. Then, the mixture filtered and the polymer purified using Soxhlet extraction with 300 mL each of methanol, acetone, hexane, toluene and chloroform. The toluene and chloroform fractions were concentrated to about 50 mL and then put into 300 mL of methanol. After the mixture was stirred overnight, the pure polymer was obtained by filtration to yield PDTSDTBTDI-DMO as blue powders, (42.0 mg, 0.045 mmol, 33.90% yield) of toluene fraction, (72.0 mg, 0.077 mmol, 58.12% yield) of chloroform fraction with total yield 92.02%. GPC: Toluene fraction, \(M_{\rm n}\) = 6200 g mol\({}^{-1}\), \(M_{\rm w}\) = 20,600 g mol\({}^{-1}\), PDI = 3.2 and Dp = 7; chloroform fraction, \(M_{\rm n}\) = 14,600 g mol\({}^{-1}\), \(M_{\rm w}\) = 79,900 g mol\({}^{-1}\), PDI = 5.4 and Dp = 16. \({}^{1}\)H NMR (toluene fraction) (C\({}_{2}\)D\({}_{2}\)Cl\({}_{4}\), 8): 8.16-8.01 (bm, 2H), 7.54-7.17 (bm, 4H), 3.87-3.65 (bm, 2H), 1.81-1.67 (bm, 1H), 1.60-1.50 (bm, 3H), 1.48-1.07 (bm, 3H), 1.05-0.94 (bm, 6H), 0.89-0.78 (bm, 10H). FT-IR (cm\({}^{-1}\)): 3129, 3062, 2955, 2923, 2848, 1753, 1696, 1546, 1510, 1425, 1400, 1350, 1168, 1104, 1068, 1011, 897, 836, 793, 761, 743, 688. Elemental analysis (%) calculated for C\({}_{50}\)H\({}_{61}\)N\({}_{3}\)O\({}_{2}\)S\({}_{5}\)Si: C, 64.96; H, 6.65; N, 4.55; S, 17.34. Found: C, 63.29; H, 6.49; N, 4.74; S, 17.10.  
**Synthesis of poly[4,4-dicotyl-2,6-dithieno[3,2-b2,3'-d]silo-alt-5,5-(4,7'-bis(2-thienyl)-2,7,1',3'-benzothiadiazole-5,6-N-octyl-dicarboxylic imide) (PDSTDBTDI-8): PDTSDTBTDI-8)** was synthesized following the same synthesizing procedure for PDTSDTBTDI-DMO: (91.0 mg, 0.143 mmol) of M2 and (107.0 mg, 0.143 mmol) of M3 were copolymerized using (2.3 mg, 0.01 mmol) of Pd(OAc)\({}_{2}\) and (6.5 mg, 0.021 mmol) of P(o-tol)\({}_{3}\) in 5 mL anhydrous toluene at 110 \({}^{\circ}\)C for 72 h. (73.0 mg, 0.081 mmol, 57.00%yield) of PDTSDTBTDI-8 was obtained as blue powders. GPC: toluene fraction, \(M_{\rm n}\) = 5700 g mol\({}^{-1}\), \(M_{\rm w}\) = 14,000 g mol\({}^{-1}\), PDI = 2.4 and Dp = 6. \({}^{1}\)H NMR (toluene fraction) (C\({}_{2}\)D\({}_{2}\)Cl\({}_{4}\), 8): 8.19-8.01 (bm, 2H), 7.55-7.20 (bm, 4H), 3.87-3.66 (bm, 2H), 1.841.64 (bm, 2H), 1.61-1.07 (bm, 34H), 1.06-0.92 (bm, 3H), 0.89-0.78 (bm, 10H). FT-IR (cm\({}^{-1}\)): 3129, 3062, 2951, 2919, 2851, 1749, 1689, 1549, 1514, 1425, 1403, 1350, 1161, 1007, 893, 836, 793, 747, 686. Elemental analysis (%) calculated for C\({}_{48}\)H\({}_{57}\)N\({}_{3}\)O\({}_{2}\)S\({}_{5}\)Si: C, 64.32; H, 6.41; N, 4.69; S, 17.88. Found: C, 63.09; H, 6.19; N, 5.11; S, 17.63.