Impact of dye end groups on acceptor–donor–acceptor type molecules for solution-processed photovoltaic cells

Two new oligothiophene derivatives of the acceptor-donor-acceptor type, incorporating double rhodanine or 1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione units as the terminal acceptor groups, D2R(8 + 2)7T and DTDMP7T, have been designed and synthesized for solution-processable small molecule BHJ solar cells. The impacts of these different end dye moieties on their optical, electrochemical properties, morphology, mobility and solar cell performance were studied. Both compounds exhibit broad and highly efficient solar absorption with low bandgaps of 1.70 and 1.62 eV for D2R(8 + 2)7T and DTDMP7T, respectively. The D2R(8 + 2)7T and DTDMP7T based BHJ solar cell devices achieved a PCE of 2.46% and 4.05%, respectively, under the illumination of AM.1.5, 100 mW cm super(-2).