Cu3Se2 counter electrode with rGO interlayer by pulsed electrodeposition for quantum dot-sensitized solar cells

We synthesized a reduced graphene oxide/copper selenide (rGO/Cu3Se2) cumulative structure on a fluorine doped tin oxide (FTO) conducting glass substrate. The pulsed electrodeposition method was used to construct the rGO and Cu3Se2 nanostructures. During rGO deposition, pulsed electrodeposition resulted in a uniform film on the FTO. Deposited rGO with surface defects can act as an active site for Cu3Se2 growth. In the case of Cu3Se2, pulsed electrodeposition contributed to its uniform stoichiometry and porous structure. This porosity affected the efficient diffusion of liquid electrolytes toward the counter electrode surface and resulted in high power conversion efficiency. In addition, the rGO interfacial layer served as electron shuttle, directly prohibited the recombination path between the FTO and electrolyte and enhanced the fill factor (FF). As a result, the FTO/rGO/Cu3Se2 electrodes with CdS/CdSe/ZnSe QD photoanodes achieved a power conversion efficiency of 3.622%, which was a significant improvement over the 2.997% efficiency of direct-deposited FTO/Cu3Se2 electrodes with the same photoanodes.