Quantum-Dot Sensitized Solar Cells Employing Hierarchical Cu2S Microspheres Wrapped by Reduced Graphene Oxide Nanosheets as Effective Counter Electrodes

Hierarchical Cu2S microspheres wrapped by reduced graphene oxide (RGO) nanosheets are prepared via a one-step solvothermal process. The amount of graphene oxide used in the synthesis process has a remarkable effect on the features of Cu2S microspheres. Compared to Pt and Cu2S electrodes, RGO-Cu2S electrodes show better electrocatalytic activity, greater stability, lower charge-transfer resistance, and higher exchange current density. As expected, RGO-Cu2S electrodes exhibit superior performance when functioning as counter electrodes in CdS/CdSe quantum-dot sensitized solar cells (QDSSCs) using a polysulfide electrolyte. A power conversion efficiency up to 3.85% is achieved for the QDSSC employing an optimized RGO-Cu2S counter electrode, which is higher than those of the QDSSCs featuring Pt (2.14%) and Cu2S (3.39%) counter electrodes.