Versatile displays based on a 3-dimensionally ordered macroporous vanadium oxide film for advanced electrochromic devices

Three-dimensionally ordered macroporous (3DOM) vanadium oxide film was fabricated by anodic deposition of vanadium oxide into colloidal crystal template. The as-prepared films were investigated by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The electrochemical and electrochromic behaviors of the films were studied in 1.0 M LiClO₄-propylene carbonate solution. Because of the larger surface area and shorter diffusion distance, the 3DOM film exhibited better electrochromic performance than the dense film prepared without the template. The 3DOM film exhibited multicolor changes (yellow, green and black) in the voltage window from +1 to -1 V with a high transmittance modulation of ca. 34% at 460 nm and high switching speed (1.5 s for coloration and 2.1 s for bleaching). Cyclic voltammetry (CV) and chronoamperometry measurements showed that the 3DOM structure is beneficial for Li⁺ diffusion in vanadium oxide films. An ITO/vanadia/gel/PEDOT:PSS/ITO electrochromic device was assembled, and the device showed multicolor changes with fast switching speed (3.5 s for anodic coloration and 3.4 s for cathodic coloration) and good cycling stability.