Efficient electrochromic efficiency and stability of amorphous/crystalline tungsten oxide film

Electrochromic material is a reversible color change material under applied electric field and the adjustable spectrum range is significantly wide. As an inorganic electrochromic material, WO3 has the characteristics of high color contrast and easy synthesis. Despite said characteristics, the poor stability and low electrochromic efficiency of single WO3 films limit the application. In the present study, compositing amorphous WO3 (a-WO3) on crystalline WO3 (c-WO3) is proposed, so as to form composite film and improve the electrochromic properties. The synergistic mechanism of crystalline and amorphous WO3 was analyzed and the synergistic effect on improving the electrochromic properties of film was investigated. Li+ diffusion of the amorphous/crystalline WO3 (a-WO3/c-WO3) film (13.3956 × 10−12 cm2/s) was more than three times that of the c-WO3 film (4.3681 × 10−12 cm2/s). At the same time, the coloring time, bleaching time of the a-WO3/c-WO3 film were 30%, 37% shorter, respectively, than the c-WO3 film, and the electrochromic efficiency of the a-WO3/c-WO3 film was 40% higher than the c-WO3 film. The detailed experimental data reveal that the film had high electrochromic properties due to the crystalline WO3 enhancing the cyclic stability and the amorphous WO3 enhancing the ion storage and transport capabilities. The strategy of controlling the crystallinity to form a composite film enhanced the electrochromic properties, and is a promising method for electrochromic study in the future.