Hexacyclic lactam building blocks for highly efficient polymer solar cells

Two hexacyclic lactam building blocks, TD1 and TD2, and four D-A copolymers have been developed. Compared with thiophene copolymers, selenophene analogues PSeTD1 and PSeTD2 possess medium optical bandgaps, better packing, higher hole mobilities, enhanced EQE, and higher J(sc). Inverted PSeTD2:PC71BM solar cells exhibited a decent PCE of 8.18%, which is a record for D-A copolymers using selenophene as the donor unit.