Impact of symmetry-breaking of non-fullerene acceptors for efficient and stable organic solar cells.

The concurrent enhancement of short-circuit current ( ) and open-circuit voltage ( ) is a key problem in the preparation of efficient organic solar cells (OSCs). In this paper, we report efficient and stable OSCs based on an asymmetric non-fullerene acceptor (NFA) IPC-BEH-IC2F. The NFA consists of a weak electron-donor core dithienothiophen[3,2-]-pyrrolobenzothiadiazole (BEH) and two kinds of strong electron-acceptor (A) units [9-indeno[1,2-]pyrazine-2,3-dicarbonitrile (IPC) with a tricyclic fused system and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1-inden-1-ylidene)malononitrile (IC2F)].