The electrochromic properties of the film enhanced by introducing oxygen vacancies to crystalline tungsten oxide

Abstract

Electrochromism refers to a reversible discoloration phenomenon of some materials under the action of electric field. Simple WO3 has many advantages as an electrochromic material, but its application is limited for low coloration efficiency (CE). For this, the study proposed a solution as follows for the first time: With the high temperature atmosphere method, prepare crystalline WO3 with oxygen vacancies as the film to improve the electrochromic performance. In the study, the effect of an optimal number of oxygen vacancies for improving the electrochromic performance of the film as well as relevant mechanism was studied by a comparative experiment. The Li+ diffusion coefficient of the film with an optimal number of oxygen vacancies (c-WO3−x (2 h)) was 30% higher than that of simple c-WO3 film. At the same time, as compared with c-WO3 film, c-WO3−x had color rendering time and bleaching time shortened by 96.5% and 16% respectively. Relevant experimental data have shown that the film with an optimal number of oxygen vacancies has a relatively high electrochromic performance. The reason for this is as follows: For the crystalline WO3 as substrate, there are oxygen vacancies that may generate impurity band between valence band and conduction band of a semiconductor electrode material, decrease the band gap, and reduce the energy required for electron transition to the conduction band, thus improving the electrochromic performance of the film. Forming a film to improve the electrochromic performance through preparing crystalline WO3 with oxygen vacancies is a promising method for the future research on electrochromism.