Flexible electrochromics: magnetron sputtered tungsten oxide (WO3−x) thin films on Lexan (optically transparent polycarbonate) substrates

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Tungsten oxide (WO 3− x ) based electrochromics on flexible substrates is a topic of recent interest. The present communication reports the electrochromic properties of WO 3− x thin films grown on lexan, an optically transparent polycarbonate thermoplastic substrate. The WO 3− x films are prepared at room temperature (300 K) by the reactive DC magnetron sputtering technique. The physical properties of metal oxide thin films are known to be controlled by the oxygen stoichiometry of the film. In the present work, the WO 3− x thin films are prepared by varying the oxygen flow rates. All the WO 3− x thin films are amorphous in nature. The electrochromic performance of the WO 3− x thin films is evaluated by cyclic voltammetry measurements on tin doped indium oxide (ITO) coated lexan and glass substrates. The optical band gap of WO 3− x thin films grown on lexan substrates (at any given oxygen flow rate) is significantly higher than those grown on glass substrates. The coloration efficiency of WO 3− x thin films (at an oxygen flow rate of 10 sccm) on lexan substrates is: 143.9 cm 2 C −1 which is higher compared to that grown on glass: 90.4 cm 2 C −1 .