The design of highly efficient polymer solar cells with outstanding short-circuit current density based on small band gap electron acceptor

摘要

To extend the absorption and enhance the electron mobility of fused-ring electron acceptors (FREAs), we designed and synthesized new FREAs (TTIC and TTIC-M) based on 4,9-dihydrothieno[3',2':4,5]cyclopenta[1,2-b] thieno[2 '',3 '':3',4'] cyclopenta[1',2':4,5]thieno[2,3-d]thiophene (DTCTT) and 1,1-dicyanomethylene-3-indanone (IC). DTCTT unit possesses strong electron donating ability, which can broaden the absorption of the resulting acceptor molecule by enhanced internal charge transfer (ICT) effect. The S atoms on the fused ring structure can enhance the electron transport by intermolecular noncovalent S-S interaction. Furthermore, the introduction of a methyl group at the terminal IC unit can elevate the LUMO energy level of FREAs and afford higher open circuit voltage (V-oc).