A D–A polymer, PSeTPTI, was developed by copolymerizing a pentacyclic acceptor unit TPTI with a selenophene unit. PSeTPTI possesses a narrow optical bandgap, a low-lying HOMO energy level, and a high hole mobility of 0.26 cm2 V−1 s−1. PSeTPTI/PC71BM solar cells demonstrate a PCE of 6.04%, which is the highest efficiency for the conjugated copolymers using selenophene as the donor unit.
