Investigation of the Effect of O2/Ar Ratio on Flexible WO3 Electrochromic Films Prepared by Magnetron Sputtering and Performance Optimization via Ti Doping

In this study, WO3 thin films were prepared on PET/ITO flexible substrates via magnetron sputtering, and the effects of the O2/Ar ratio on the microstructure and electrochromic performance were systematically investigated. Furthermore, Ti doping was introduced under optimal conditions to further enhance the performance. The results indicate that the O2/Ar ratio significantly influences ion transport and charge storage behavior by regulating the short-range order, surface morphology, and oxygen vacancy concentration of the films. When the O2/Ar ratio is 20:80, an optimal balance between structural ordering and defect concentration is achieved, leading to the best electrochromic performance, with an average optical modulation of 61.44% in the visible range. On this basis, Ti doping further optimizes the electronic structure and defect distribution of the films. Under optimal conditions, dual-band electrochromic modulation in both the visible and near-infrared regions is achieved (71.53%/53.41%), while simultaneously reducing interfacial charge transfer resistance and enhancing ion insertion capability. Moreover, the Ti-doped film retains 91.12% of its initial optical modulation after 1000 coloration/bleaching cycles, demonstrating excellent cycling durability. This study reveals the regulatory mechanism of the O2/Ar ratio on the structure and electrochromic performance of flexible WO3 thin films, elucidates the role of Ti doping in performance enhancement, and demonstrates a competitive combination of optical modulation, electrochemical kinetics, and cycling stability among recently reported flexible WO3-based electrochromic films, providing a theoretical basis for the design of high-performance flexible electrochromic films.