Branched thiophene-based oligomers as electron acceptors for organic photovoltaics

Two branched V-shaped benzo[b]thiophene-based structures were investigated as novel electron-acceptor materials in blended photovoltaic devices. Photoinduced charge transfer was demonstrated in blends between a regioregular poly(3-hexylthiophene) and the oligothiophenes, via photoluminescence spectroscopy. The enhanced photovoltaic performance exhibited by the blended cells, with respect to that of pristine devices in which the polymer was the active layer, represented further evidence for exciton dissociation. Remarkable improvement of the performance of the blended devices upon mild thermal annealing was achieved. Furthermore, the effect of the molecular structure of the branched benzo[b]thiophenes on the blend photoresponse is discussed.