A low band-gap polymer based on unsubstituted benzo[1,2-b:4,5-b ']-dithiophene for high performance organic photovoltaics

A low band-gap conjugated polymer, PBDTDPP, composed of unsubstituted benzo[1,2-b:4,5-b']dithiophene and diketopyrrolo-[3,4-c]pyrrole was synthesized. The deep HOMO level of PBDTDPP enhances the V-OC of a PSC up to 0.82 V and exhibits a PCE of 5.16%, while alkoxy substituted PBDTDPP-OR yields a PCE of 2.24% with a V-OC of 0.61 V.