Electrochromic properties of NiOxHy thin films

NiOxHy films were prepared by DC magnetron sputtering in H2/O2 atmosphere. NiOxHy coatings with transparency and high electrochromic efficiency were obtained by changing H2 content. A 60 nm thick NiOxHy film with transmittance of 0.57 (as-deposited state), 0.78 (bleached state) and 0.24 (coloured state) at wavelength of 550 nm was deposited in an atmosphere of H2(60%)+O2(40%). Analysis of infrared spectra (6000∼2400 cm−1) showed that the absorption peaks for bleached and colored states are associated with free ‘OH’ and OH stretching vibrations, respectively. XPS Ni2p core level spectra of colored NiOxHy film exhibited a peak at 856.2±0.2 eV which is attributed to Ni3+. Ni2p core level spectra of the bleached and as-deposited films exhibited two peaks at 856.4±0.2 and 854.6±0.2 eV which are attributed to Ni3+ and Ni2+.