The chemical design of a polymer can be tailored by a random or a block sequence of the comonomers in order to influence the properties of the final material. In this work, two sequences, PCPDTBT and F8BT (F8), were polymerized to form a block or a random copolymer. Differences between the various polymers were examined by exploring the surface topography and charge carrier mobility. A distinct surface texture and a higher charge carrier mobility was found for the block copolymer with respect to the other materials. Solar cells were prepared with polymer:PC71BM blend active layers and the best performance of up to 2% was found for the block copolymer, which was a direct result of the fill factor. Overall, the sequences of different copolymers for solar cell applications were varied and a positive impact on efficiency was found when the block copolymer structure was utilized. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012