Substrate temperature-controlled amorphous-crystalline hybrid structure in tungsten oxide thin films for comprehensive high-efficiency electrochromic performance

Tungsten oxide (WO₃), as a typical cathodic electrochromic material, exhibits high coloration efficiency and cost-effectiveness, yet faces a critical performance trade-off between the poor cycling stability of amorphous structures and the limited ion transport efficiency of crystalline films. In this study, monoclinic phase-dominated amorphous-crystalline hybrid WO₃ thin films were fabricated via reactive DC magnetron sputtering under controlled substrate temperatures. The results demonstrate that the film deposited at 350 °C achieves an optical modulation amplitude of 87.8 % at 633 nm, a coloration efficiency of 119.05 cm²/C, and over 99 % retention of optical modulation after 1000 cycles, unveiling a synergistic mechanism where crystalline frameworks suppress structural relaxation while amorphous channels facilitate rapid ion migration. These findings provide both theoretical and experimental foundations for the controllable fabrication of comprehensive high-efficiency electrochromic devices.