Low band gap benzothiophene-thienothiophene copolymers with conjugated alkylthiothieyl and alkoxycarbonyl cyanovinyl side chains for photovoltaic applications.

Alkylthiothieyl substituted benzothiophene (BDT) and alkoxycarbonyl cyanovinyl modified thienothiophene (TT) were copolymerized to obtain a new two dimensional low band gap polymer PBDTTT-S-CN, which exhibited a promising efficiency of 7.0% in organic solar cells.