High capacity and contrast of electrochromic tungsten-doped vanadium oxide films

The present paper introduced a kind of novel tungsten-doped vanadium oxide xerogel films with high electrochromic performances, which were prepared by the Sol–gel and hydrothermal route for electrochromic electrodes. The morphologies, microstructures and properties of the films were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectra (XPS), Scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), UV–vis spectra and Cyclic Voltammogram (CV). The results indicated that the films have a layered structure, and the proper amount of W can remarkably increase the ion storage capacity and improve the transmission modulation of the films. The films displayed a reversible multichromism (orange ↔ green ↔ blue ↔ brownish gray) upon Li+ insertion/extraction. The best electrochromic performance was observed for the W/V-oxide film with molar ratio W/V = 0.1. The inserted and extracted charge densities of the film can reach maximum values of 45.24 mC/cm2 and 45.2 mC/cm2 after the 20th cycle, respectively, which is approximately 4 times higher than that of pure vanadium oxide xerogel film. And the transmission modulation (ΔT) was improved to as large as 79.4% at 730 nm.