Tunable Oxygen Vacancies and Porous Structure of Ta-Doped Tungsten Oxide Films for Enhanced Electrochromic Properties

Tungsten oxide (WO3), as a typical electrochromic material, is well-known for its high coloration efficiency, wide optical modulation range, and excellent cyclic stability. In this study, tantalum (Ta)-doped WO3 films were fabricated by using the sol–gel method. The effects of Ta doping on the morphology and oxygen vacancy concentration of WO3 films were systematically investigated, along with how these factors influence their electrochromic performance. The results demonstrate that Ta doping significantly enhances the optical modulation (82.9% at 750 nm), accelerates the response time (5.0 s for coloring and 4.5 s for bleaching), and improves the optical reversibility of WO3 films compared to undoped WO3 films. Remarkably, the Ta-doped WO3 films exhibit substantial optical modulation in both the visible and the near-infrared regions, achieving outstanding dual-band electrochromism.