NiOx thin films were prepared using dc magnetron reactive sputtering in the various pressures of oxygen. They were subsequently hydrated to obtain NiOxHy by treatment in the aqueous KOH. Electrochemical characterization of NiOxHy thin films were measured

and spectral normal transmittance and near normal reflectance for bleached state and coloured state of NiOxHy thin films were measured in 0.35〈λ〈2.5μm wavelength range. Sputtering oxygen pressure dependence of average luminous transmittance

reflectance and absorptance on the bleached and coloured state was derived. The absorption coefficients for near optimum sample vs wavelength and electrochromatic mechanism were discussed.