Acceptor–acceptor conjugated copolymers based on perylenediimide and benzothiadiazole for all‐polymer solar cells

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 π-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 π–π 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. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1200–1215