Electrochromic device application of tungsten oxide film with polymer electrolytes

• WO3 films are obtained by electrodeposition of WCl6 precursor.
• The procedure for electrodeposition is a new avenue to prepare tungsten oxide films.
• This flowchart for electrodeposition is simple and fast.
• Liquid and solid Nafion is used as electrolyte in ECD.
• WO3 films offer extraordinarily high optical modulation in liquid Nafion electrolyte.

We have compared tungsten chloride, peroxotungstic acid and acetylated peroxotungstic acid precursors in terms of their efficiency to prepare tungsten oxide thin films in our recent work. Therein, our results indicated the superiority of tungsten hexachloride over the others, in the sense that the formation of the film requires shorter deposition time of film and lower potential of deposition, when the former is of choice. Moreover, these films allow a higher extent of ion intercalation/deintercalation, resulting in superior electrochromic performance. Encouraged by these results, we turned our attention to the preparation of electrochromic devices wherein both liquid and solid Nafion functioned as the electrolytic layer. Our results primarily indicate that these devices offer a large optical modulation (i.e., the color of the device switches from dark blue to a fully transparent state with the applied potential) in liquid Nafion electrolyte. More importantly, the use of liquid Nafion in conjunction with its solid form functioned as a kind of network between layers, by facilitating intercalation/deintercalation of ions. If the full EC device is desired to be fabricated, electrochromic properties of the device can be effortlessly modulated by adding ion storage layer or altering the material of EC layer. Overall, we report that this configuration presents an easy and expeditious way of preparing electrochromic devices.

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