Tunable OxygenVacancies and Porous Structure of Ta-DopedTungsten 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.