Increasing polymer solar cell active layer efficiency and organization by adding gold-functionalized reduced graphene oxide

Relatively low efficiency is one of the main obstacles to overcome in the engineering of organic bulk heterojunction (BHJ) solar cells. Reduced graphene oxide (RGO), which has high conductivity, has been proposed to enhance the function of PCBM in the interfacial dissociation of excitons, but incorporating it into the hydrophobic photoactive polymers has proved challenging. Here we describe a novel technique for incorporating Au nanoparticles (AuNp) into the structure of the RGO. The AuNps then interact with the sulfur groups on the photoactive polymer component, while the RGO interacts via n - n stacking with the chemically similar PCBM, thereby anchoring the complex to the polymer interface. Graphene oxide was synthesized and then reduced in the presence of a gold salt. The resulting gold-functionalized RGO (AuRGO) sheets were characterized using TGA, FTIR, and TEM. The AuRGO was not soluble in chlorobenzene; however, in the presence of P3HT, the AuRGO dissolved, suggesting a reaction between the gold and the sulfur of the P3HT via a metal-thiolate bond. At 2 mg/ml, AuRGO increased the solar cell efficiency approximately 50% over the control, but higher concentrations produced large, columnar structures which blocked the electrode from having a uniform contact with the active layer.