Two kinds of low-band gap polymers, poly[{N-(1-octyldecyl)-2,7-carbazole)}-alt-{1,7- di(4-tert-butylphenyloxy)-3,4,9,10-perylenebis(dicarboximide)-N,N-di(2,6-dimethyl- phenyl-4-yl)}] poly(Cvz-PDIMEP) and poly{[N,N-di(10-nonadecyl)perylene-3,4,9, 10-tetracarboxylic acid diimide-1,7-diyl]-alt-(9-heptadecyl)-9H-carbazol-2-yl)} poly (Cvz-PDIC9), were synthesized by palladium-catalyzed Suzuki polymerization. Bulk heterojunction solar cells with an ITO/PEDOT/polymer:PC71BM/LiF/Al configuration were fabricated, which shows short-circuit current density, open-circuit voltage, fill factor, and power conversion efficiency of 0.85mA/cm(2), 0.32V, 0.27, and 0.073% under AM 1.5 irradiation (100 mW/cm(2)), respectively.