Nanostructured NiOx-coated TiO2 electrodes for dye-sensitized solar cells

NiOx nanostructures are employed to modify the nanoporous TiO2 photoanode for dye-sensitized solar cells with the surface sol-gel process by multiple spin coating. X-ray photoelectron spectroscopy confirms that the chemical states for the as-prepared NiOx nanostructures are more diverse than those derived by magnetron sputtering. Combined with SEM-EDX results, the structure of NiOx layer cannot be interpreted a uniform "thin film", but as incomplete coating with a few particulate nickel oxides. The results of dark current measurement and electro-chemical impedance spectroscopy analysis suggest that an energy barrier is formed at the interface of electrode and electrolyte by the coated NiOx layers. The basic NiOx-coated surface favors dye attachment, leading to a dramatic enhancement in the amount of adsorbed dye onto the TiO2 surface. It also demonstrates that an energy conversion efficiency of 6.64% could be achieved for the NiOx-coated TiO2 electrode with three spin-coated layers of NiOx which accounts for a 27% increment in energy conversion efficiency over that for the unmodified TiO2 electrode.