Properties of WO_3-x Electrochromic Thin Film Prepared by Reactive Sputtering with Various Post Annealing Temperatures

Abstract

The WO 3- x thin films were prepared on indium tin oxide (ITO) coated glass at 0.7 oxygen flow ratio [O 2 /(Ar+O 2 )] using the facing targets sputtering (FTS) system at room temperature. In order to obtain the annealing effect, as-deposited thin films were annealed at temperatures of 100, 200, 300, 400, and 500 °C for 1 h in open air. The structural properties of the WO 3- x thin film were measured using an X-ray diffractometer. The WO 3- x thin films annealed at up to 300 °C indicated amorphous properties, while those annealed above 400 °C indicated crystalline properties. The electrochemical and optical properties of WO 3- x thin films were measured using cyclic voltammetry and a UV/vis spectrometer. The maximum value of coloration efficiency obtained was 34.09 cm 2 /C for thin film annealed at 200 °C. The WO 3- x thin film annealed at 200 °C showed superior electrochromic properties.