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/cm(2) and 45.2 mC/cm(2) after the 20th cycle, respectively, which is approximately 4 times higher than that of pure vanadium oxide xerogel film. And the transmission modulation (Delta T) was improved to as large as 79.4% at 730 nm. (c) 2008 Elsevier B.V. All rights reserved.