Preparation and properties of all solid-state electrochromic devices based on tungsten oxide nanocomposites

The optical properties of electrochromic materials can change reversibly under an applied voltage. Tungsten oxide has been widely used in various fields because of its excellent electrochromic efficiency. The electrochromic films produced by W18O49 nanowires and WO3 have excellent performance. Compared with WO3 film, the porous structure of the nanowires can make ions rapidly diffuse, provide a larger surface area for the charge transfer reaction, promote electrolyte penetration, and effectively improve the electrochromic efficiency. In this paper, a kind of electrochromic tungsten oxide thin film combining W18O49 nanowires and WO3 was prepared by combining a hydrothermal method and a tungstic acid method. The electrochromic performance of the film was improved considerably by combining the two kinds of thin films. The results show that the optical modulation amplitude is close to ideal (92.5%) and has a fast colour fading (colour 1.7 s and colour fading 1.3 s) effect, a good cycle stability, which is much better than those of the WO3 and W18O49 films. Using lithium perchlorate and PC as raw materials and polyurethane as a photocuring agent, a solid-state electrochromic device based on a tungsten oxide composite film was fabricated by capillarity. The colouring time of the device is 2 s, the fading time is 1 s, and the optical modulation amplitude is 85%.