Electrochromic Properties of Ni-W Oxide Thin Films by Reactive Magnetron Sputtering

Abstract

Electrochromic ‘smart windows’, capable of dynamically adjusting light transmittance, glare and solar heat gain by an electric field have attracted more and more interests in both research laboratories and industry. Among various electrochromic materials, anodically coloring NiOx is of essential importance as the ion storage layer for building complementary electrochromic devices. In this paper, we have deposited tungsten doped NiOx thin films on indium tin oxide (ITO) coated glass substrates by reactive magnetron sputtering in a mixed gas ambient of Ar and O2. The atomic ratio of W/Ni were varied by changing the number of metal strips placed on top of the nickel oxide target. The electrochromic properties of Ni-W oxide thin films were tested & compared in a 3 electrode electro-chemical system with NaOH as liquid electrolyte. The experimental results showed that light transmittance modulation; coloration efficiency, as well as response times of the W-Ni oxide thin films can be greatly improved by controlling the ratio of W/Ni.