Highly efficient thieno[3,4-c]pyrrole-4,6-dione-based solar cells processed from non-chlorinated solvent

To obtain high performance bulk heterojunction organic solar cells, the selection of solvents to prepare the donor/acceptor blend is as important as the choice of the donor/acceptor materials themselves. State-of-the-art lab-scale polymer solar cells have evolved around chlorinated solvents such as chloroform, chlorobenzene and o-dichlorobenzene. However, for large scale applications, benign processing solvents may become inevitable. In this work, we used a mixture of Xylenes (a chlorine-free solvent), methyl naphthalene (MeN) and 1,8-diiodoctane (DIO) to modulate the nano-scale morphology of poly(4,4-bis(2-ethylhexyl)-dithieno[3,2-b:2′,3′-d]silole-alt-1,3-(5-octylthieno[3,4-c]pyrrole-4,6-dione) (PDTSTPD)/PCBM blend, one of the most efficient active layer in polymeric solar cell. Power conversion efficiencies up to 5.5% (with PC61BM) and 6.2% (with PC71BM) were obtained for photovoltaic devices with an active area of 1.0 cm2.