Photoelectrochromic Properties of TiO2-xNx/NiO Bilayer Thin Films

N-doped TiO2 films were prepared on indium fin oxide(ITO) conducting glass by dc-reactive magnetron sputtering using a Ti target in an O-2/N-2/Ar mixture gas in combination with heat-treatment at 300-500 degrees C. The microstructure, optical and photoelectrochemical properties of the as-formed films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV-Vis transmittance spectrum. Highly porous NiO was deposited onto the N-doped TiO2 layer by chemical bath deposition to obtain ITO/TiO2-xNx/NiO bilayer thin films and they exhibited excellent and noticeable photoelectrochromism. The TiO2-xNx film annealed at 400 degrees C showed the highest photocurrent response. The color of films changed from colorless to brown and the transmittance varied from 79.0% to 12.6% at 500 nm after 1 h of irradiation.