Synthesis and photovoltaic properties of two-dimensional copolymers based on novel benzothiadiazole and quinoxaline acceptors with conjugated dithienylbenzothiadiazole pendants

Two novel acceptors of benzo[c][1,2,5]thiadiazole and quinoxaline with conjugated dithienylbenzothiadiazole pendants were first designed and synthesized for building efficient photovoltaic copolymers. Based on benzo[1,2-b;3,4-b]dithiophene donors and the two acceptors, two new copolymers have been prepared by Stille coupling polymerization. The resulting copolymers were characterized by H-1 NMR, gel permeation chromatography, and thermogravimetric analysis. UV-Visible absorption and cyclic voltammetry measurements indicated that the two copolymers possessed strong and broad absorption in the range of 300-700 nm, and deep-lying energy levels of highest occupied molecular orbitals. The polymer photovoltaic devices based on benzo[c][1,2,5]thiadiazole-based copolymer/phenyl-C-71-butyric acid methyl ester exhibited a power conversion efficiency of 2.42%, attributed to its relatively better light-harvesting ability and active film morphology. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 668-677