Study On Electrochromism Of Ag-WO₃ Composite Thin Flims Prepared By RF Magnetron Sputtering

WO3 thin film is the earliest known electrochromic material and extensively investigated. The thin films have been attracting attention for having a good application prospect in smart window, display device, solar battery, and etc. However, the electrochromic performance of WO3 thin films need to be further improved and enhanced for practical application. Therefore, improving the films'performance and preparing a new type WO3 thin films with high ability have become advanced research project in the areas such as photochemistry, material science.In this paper, WO3 thin film and Ag-WO3 composite films with silver volume fraction of 3%～12% were prepared by RF magnetron co-sputtering on silicon and ITO coated glass. The microstructure, surface morphology, composition, optical properties and electrochromism of films were characterized by X-ray diffractometer, X-ray photoelectron spectroscopy, scanning electron microscope, ultraviolet-visible spectrophotometer, spectroscopic ellipsometry and electrochemical workstation, respectively. The influence of Ag components and sputtering time on the microstructure, surface morphology, composition, optical properties and electrochromic performance of films were studied.The results show that the films deposited at room temperature are all amorphous. The structure of films transformed from tetragonal phase to monoclinic phase when metallic silver was embedded into WO3 base, and the preferred orientation of composite films have been changed with the content of Ag increasing. The silver in the films is metallic Ag. The results of electrochromic test indicate that the voltage required colored decreases, the response speed is improved greatly and the film electrode reaction speed increases with the content of silver increasing. These can attribute to that the carrier concentration increase as the content of silver increase. However Ag components with high concentration degrade the cycle properties., this mainly dues to the Ag particle in films interacts with the Li+ ions which inject into the composite films, and hamper the Li+ ions come out from the colored films, leading to the bleach performance of composite films decline with the content of silver increases.In order to improve the cycle property of 6.0Vol.%Ag-WO3 composite films, the paper also discusses the influence of sputtering time on microstructure, morphology and electrochromic performance of the films. The analysis results show that the composite films are all monoclinic phase with a preferred orientation along (110) lattice plane diffraction. The electrochromic test result shows that the cycle performance of composite films prepared under the condition sputtering time is 30min has been improved significantly, the light modulation has reached 46.3%, and the respond time is 3.5s. These due to there are more porous on the films surface to be propitious to Li+ ions injection and extraction, and the films have better reversibility.The main innovations of the investigation are as follows:1. WO3 thin films modified by silver nanoparticles have been first prepared by RF magnetron sputtering, and study on the influence of Ag component on the electrochromic performance of Ag-WO3 composite films.2. Study on the influence of sputtering time on microstructure, morphology and electrochromic performance of the films, and have obtained that when the sputtering time is 30min, the 6.0Vol.%Ag-WO3 composite films have better reversibility.3. Through the above results can speculate that there is the interaction between the Ag component and Li+ ions during the electrochromic test, and provide an experimental basis for investigating the mechanism of electrochromism thin films.