Rational design of a difluorobenzo[c]cinnoline-based low-bandgap copolymer for high-performance polymer solar cells

A copolymer with A–A structure is rationally designed and synthesized by using difluorobenzo[c]-cinnoline (DFBC) as weak electron-withdrawing (A) moieties and 1,4-diketo-pyrrolo[3,4-c]pyrrole (DPP) as strong A moieties. Polymer solar cells based on PDFBC-DPP and PC71BM showed a promising power conversion efficiency of 7.92%, which is one of the highest values in polymer solar cells based on A–A structure.