Reduced graphene oxide-supported aggregates of CuInS2 quantum dots as an effective hybrid electron acceptor for polymer-based solar cells

A hybrid featuring the CuInS2 quantum dots (CuInS2-QDs) on reduced graphene oxide (rGO) sheets is synthesized by a facile one-pot solvothermal approach with thiourea as S source, in which graphene oxide (GO) sheets are reduced into rGO sheets in course of the CuInS2-QDs aggregate growth. The growth mechanism of the hybrid is elucidated. It is found that adsorption of Cu2+ cations mainly takes place at epoxy/hydroxyl groups on GO sheets at room temperature and the adsorbed Cu+ cations resulting from the Cu2+ reduction at solvothermal temperature act as the nucleation for the surface growth of CuInS2-QDs into three-dimensional aggregates on GO sheets that are simultaneously reduced into rGO sheets. Our results demonstrate that the rGO/CuInS2-QDs hybrid is an effective electron acceptor with a complementary absorption property for polymer-based solar cells. The solar cells based on rGO/CuInS2-QDs hybrid and poly(1-methoxy-4-(2-ethylhexyloxy)-p-phenylene vinylene) exhibit an efficiency of 1.5%, much higher than the counterpart devices of rGO sheets. The effects of CuInS2-QDs aggregates on device performance are discussed. In the long run, this work provides a potential hybrid electron acceptor for low-cost and efficient solar cell fabrication.