Graphene-based copper oxide thin film nanostructures as high-efficiency photocathode for p-type dye-sensitized solar cells

Graphene-based p-type dye-sensitized solar cells (p-DSSCs) have been proposed and fabricated using copper oxide urchin-like nanostructures (COUN) as photocathode with an FeS₂ counter electrode (CE). COUN composed of Cu₂O core sphere and CuO shell nanorods with overall diameters of 2 to 4μm were grown by a simple hydrothermal method with self-assemble nucleation. It was figured out that the formation of copper oxide core/shell structures could be adjusted by an ammonia additive leading to pH change of the precursor solution. In addition to a photocathode, we also demonstrated FeS₂ thin films as an efficient CE material alternative to the conventional Pt CEs in DSSCs. FeS₂ nanostructures, with diameters of 50 to 80 nm, were synthesized by a similar hydrothermal approach. FeS₂ nanostructures are demonstrated to be an outstanding CE material in p-DSSCs. We report graphene/COUN as photocathode and Pt/FeS₂ as CE in p-DSSCs, and results show that the synergetic combination of electrodes in each side (increased interconnectivity between COUN and graphene layer, high surface area, and high catalytic activity of FeS₂) increased the power conversion efficiency from 1.56% to 3.14%. The excellent performances of COUN and FeS₂ thin film in working and CEs, respectively, make them unique choices among the various photocathode and CE materials studied.