Electrochromic properties of W_1–x–yNi_xTi_yO₃ thin films made by DC magnetron sputtering

We investigated the electrochromic properties of tungsten–nickel–titanium oxide (W_1–x–yNi_xTi_yO₃) thin films. Special emphasis was put on W_0.83–xNi_xTi_0.17O₃ since this composition gave the highest electrochemical durability. The films were deposited onto indium–tin oxide coated glass by reactive DC magnetron sputtering, and cyclic voltammetry as well as optical transmittance measurements were performed in an electrolyte of 1 M LiClO₄ in propylene carbonate. The potential window was chosen so as to cause rapid degradation of the samples. Elemental compositions were obtained by Rutherford backscattering spectroscopy and structural information by X-ray diffraction. We verified that the titanium additive improved the electrochemical durability of tungsten-oxide-based films and also documented that a further addition of nickel was unable to enhance the EC performance to any significant degree.