Silole-containing conjugated polymers (P1 and P2) carrying methyl and octyl substituents, respectively, on the silicon atom were synthesized by Suzuki polycondensation. They show strong absorption in the region of 300-700 nm with a band gap of about 1.9 eV. The two silole-containing conjugated polymers were used to fabricate polymer solar cells by blending with PC(61)BM and PC(71)BM as the active layer. The best performance of photovoltaic devices based on P1/PC(71)BM active layer exhibited power conversion efficiency (PCE) of 2.72%, whereas that of the photovoltaic cells fabricated with P2/PC(71)BM exhibited PCE of 5.08%. 1,8-Diiodooctane was used as an additive to adjust the morphology of the active layer during the device optimization. PCE of devices based on P2/PC(71)BM was further improved to 6.05% when a TiO(x) layer was used as a hole-blocking layer. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4267-4274, 2011