Preparation of electrochromic tungsten oxide thin film by sol-gel process

Abstract

A new method is shown for lower temperature preparation of tungsten oxide thin film by sol-gel process without using a catalyst, but using tungsten chloride (WCl6) as the starting material and ethanol as a solvent. When WCl6 dissolved in ethanol, tungsten ions and ethanol formed tungsten ethoxides. Thin films prepared from the solution above 300°C did not contain organics or chloride. Tungsten oxide (WO3) crystallized at temperatures above 350°C. The electrical and optical properties of the thin films were measured. Amorphous thin films showed electrochromism, but polycrystalline thin films did not. The relative transmittance of the amorphous thin films decreased to 45% on application of 3 V for 1 s.