A note on fast protonic solid state electrochromic device: NiOx/Ta2O5/WO3−x

In the present investigation, the electrochromic properties of a fast protonic solid state device: NiOx/Ta2O5/WO3−x prepared at room temperature (300 K) is reported. The non-stoichiometric tungsten oxide thin film is prepared by reactive DC magnetron sputtering technique on ITO coated glass; the oxides of tantalum (∼300 nm) and nickel (∼100 nm) are prepared by electron beam evaporation. This proton device has a coloration efficiency of ∼82.4 cm2/C and coloration and bleaching time of 6 and 5 s, respectively, and a transmittance variation of 60%. The work function of WO3−x thin films by Kelvin probe in uncolored and colored states are 4.73 and 4.30 eV, respectively.