Donor-acceptor (D-A) conjugated copolymers are one of known classes of organic optoelectronic materials and have been well developed. However, less attention has been paid on acceptor-acceptor (A-A) conjugated analogs. In this work, two types of A-A conjugated copolymers, namely P1-Cn and P2-Cn (n is the carbon number of their alkyl side chains), were designed and synthesized based on perylenediimide (PDI) and 2,1,3-benzothiadiazole (BT). Different from P1-Cn, P2-Cn polymers have additional acetylene -spacers between PDI and BT and thus hold a more planar backbone configuration. Property studies revealed that P2-Cn polymers possess a much red-extended UV-vis absorption spectrum, stronger - interchain interactions, and one-order larger electron mobility in their neat film state than P1-Cn. However, all-polymer solar cells using P1-Cn as acceptor component and poly(3-hexyl thiophene) or poly(2,7-(9,9-didodecyl-fluoene)-alt-5,5-(4,7-dithienyl-2-yl-2,1,3-benzothiadiazole) as donor component exhibited much better performance than those based on P2-Cn. Apart from their backbone chemical structure, the side chains were found to have little influence on the photophysical, electrochemical, and photovoltaic properties for both P1-Cn and P2-Cn polymers. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1200-1215