A new oligobenzodithiophene end-capped with 3-ethyl-rhodanine groups for organic solar cells with high open-circuit voltage

A new solution-processable small-molecule donor material, named DRBDT3, comprised of oligobenzo[1,2-b:4,5-b'] dithiophene as the backbone and 3-ethyl-rhodanine as the end-capped group has been designed and synthesized for application in organic photovoltaic cells. The oligobenzodithiophene derivative exhibits an absorption band from 300 to 640 nm. The film of DRBDT3 shows highly long-range ordering assembly and high mobility of 1.21x10(-4) cm(2) V-1 s(-1). The new molecule shows a deep highest-occupied molecular orbital energy level. The device based on DRBDT3 as the donor and PC71BM as the acceptor exhibits a power conversion efficiency of 4.09% with a high open-circuit voltage of 0.99 V under AM.1.5G illumination (100 mW cm(-2)).