Efficient small molecule bulk heterojunction solar cells with high fill factors via introduction of π-stacking moieties as end group

Three new oligothiophene derivatives with an acceptor-donor-acceptor structure incorporating 1,3-indanedione or the derivative of 1,3-indanedione units as the terminal acceptor groups-DIN7T, DINCN7T and DDIN7T-have been designed and synthesized for solution-processable small molecule BHJ solar cells. The impacts of these different end dye moieties on the optical absorption, solubility, electrochemical properties, morphology, mobility and solar cell performance were studied. All three compounds exhibit broad and highly efficient solar absorption with a low bandgap. The DIN7T-based BHJ solar cell device achieved a PCE of 4.93% and a high fill factor of 0.72, under illumination of AM 1.5, 100 mW cm(-2).