Well-aligned ZnO nanorod array covered with ruthenium layers for alternative counter electrodes in dye-sensitized solar cells

As an alternative material for conventional counter electrodes (CEs), which are usually made from Pt/fluorine doped tin oxide (FTO), well aligned ZnO nanorod arrays have great potential, their extremely high surface area can significantly increase the number of interfacial reaction sites in contact with the electrolyte. However, in order to use ZnO nanorod arrays as CEs, inferior charge collecting efficiency is a crucial obstacle that must be overcome. Here, patterned ZnO nanorod arrays are synthesized using a hydrothermal method and an Ru metal layer is deposited using a radio frequency sputtering process. We found the optimal conditions for ZnO nanorod growth that enable us to form vertically aligned ZnO nanorod arrays on only the ZnO seed layer. The Ru metal layer, coated onto the ZnO nanorod array serves both the role of the catalyst and the charge collecting electrode, its deposition process is controlled in such a way to maximize electrode performance. The results found in this study reveal the combination of Ru metal and the ZnO nanorod array has great potential as a lower cost alternative to Pt and FTO.