D-A copolymers based on a pentacyclic acceptor unit and a 3,3′-difluoro-2,2′-bithiophene for solar cells

Abstract

A D-A copolymer, P2FBTTPTI, was developed by copolymerizing a pentacyclic acceptor unit, thieno[2′,3′:5,6]pyrido[3,4-g]thieno[3,2-c]isoquinoline-5,11(4H,10H)-dione (TPTI), with 3,3′-difluoro-2,2′-bithiophene (2FBT). P2FBTTPTI possessed a low highest occupied molecular orbital (HOMO) energy level (−5.50 eV) and a good hole mobility (4.14 × 10−4 cm2·V−1·s−1). P2FBTTPTI:PC71BM solar cells gave a decent power conversion efficiency (PCE) of 7.64% and a high open-circuit voltage (V oc) of 0.95 V.