Anodized WO3–W Composite Electrochromic Films for Broadly Tunable Multicolor Displays

Inorganic electrochromic materials (ECMs) hold great promise for display applications due to their superior stability. However, their limited color modulation range remains a significant challenge. In this study, we employ a simple and efficient anodization process to incorporate structural colors into ECMs, achieving full-color displays. The fabricated WO₃–W films exhibit diverse structural colors and demonstrate broad color modulation capabilities during the electrochromic process with the main peaks/troughs in the reflectance spectra shifting by up to 240 nm. These broad color transitions are attributed to the variations in the optical parameters of the anodized WO₃ layer, including a maximum refractive index change of 0.66 (550 nm reference wavelength) and a maximum thickness expansion of 18%. These variations, driven by the insertion of guest ions, can be precisely controlled by the applied reduction potential. Our research offers technological approaches and theoretical insights for the application of inorganic ECMs in the domain of colorful displays.