Fast-switching electrochromic response of WO3 · 2H2O of plate-like particles synthesized by liquid phase deposition

Abstract

Abstract WO3 · 2H2O with the layered crystal structure was grown into films consisting of plate-like particles on indium doped tin oxide substrates by the liquid phase deposition at room temperature. The [WOF5]- complex was prepared by dissolving 0.015\xa0mol tungstic acid in 86 cc of a 2.34\xa0wt% hydrofluoric acid solution. The hydrolysis of [WOF5]- species in the presence of boric acid at room temperature was studied by 19F NMR spectroscopy to gain insight into the formation mechanism of WO3 · 2H2O. Microstructural studies revealed that the plate-like particles are single crystals with well-developed facets in octagonal shapes. The basal plane of the plate-like particles is parallel to the corner-sharing WO6 octahedra layers. The films showed a 92.7\xa0±\xa07.5\xa0cm2/C coloration efficiency and fast response electrochromic properties with a bleaching time and a coloration time of 0.6\xa0s and 2.0\xa0s, respectively. Such a fast electrochromic response was attributed to the facile migration of proton ions through the layered crystal structure of WO3 · 2H2O and the plate-like morphology of the films.