Influence of side chain regioregularity on photovoltaic performance has been investigated in bulk heterojunction solar cells based on a series of poly(3-dodecylthienylenevinylene)s (C12-PTV) and 6,6-phenyl-C61-butyric acid methyl ester (PCBM). Performance of each C12-PTV is optimized for fair comparison. It is found that regiorandomness has no detrimental effect on device performance, in sharp contrast to poly(3-hexylthiophene) (P3HT). Fully regioregular C12-PTV performs slightly poorer than less regioregular ones mainly due to its fast crystallization behavior. The results suggest that introduction of side chain regiorandomness is an effective strategy to enhance processability of certain types of polymers without a reduction in photovoltaic performance. The better polymer:PCBM weight ratio, found to be 3:7 for all C12-PTVs, and improved device performance, as compared with the literature work on the same polymer synthesized by a different method, demonstrate again the importance of the integrity of polymer main chain structure. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012