Fabrication of ZnO nanostructures sensitized with CdS quantum dots for photovoltaic application using a convenient solution method

Zinc oxide (ZnO) nanostructures sensitized with cadmium sulfide quantum dots (CdS QDs) were fabricated using a simple and inexpensive solution method. ZnO nanostructures, in the form of either nanocones or nanorods, were first grown directly from fluorine-doped tin oxide (FTO) substrates in aqueous solutions of zinc nitrate (Zn(NO3)2) and hexamethylenetetramine (HMTA, C6H12N4) under external voltages. Then, CdS QDs were attached to these ZnO nanostructures via reactions in the mixed aqueous solutions of cadmium nitrate (Cd(NO3)2) and thioacetamide (C2H5NS). Photovoltaic responses were obtained from the quantum dot sensitized solar cells (QDSSCs) in which these CdS QD-covered ZnO nanostructures were employed as the photoanodes. The morphologies of the ZnO nanostructures, which could be effectively modulated via the substrate location in the solutions during the fabrication, were found to have played an important role in determining the properties of the QDSSCs.