In Situ Activated Bi2WO6 Nanosheets with Fast-Response and Self-Bleaching Electrochromism for Automotive Antiglare Rearview Mirrors

Trailing vehicle headlight glare critically endangers nighttime driving safety, with electrochromic devices (ECDs) being the most promising solution. Nevertheless, commercial organic electrochromic materials face high cost and irreversible degradation, whereas inorganic alternatives exhibit slow response and severe memory effect, severely restricting their application in antiglare rearview mirrors. Herein, we report the electrochromic behavior of thin bismuth tungstate (T-BWO) nanosheets synthesized via a facile hydrothermal method. A unique in situ activation process is discovered, accompanied by (19.7 ± 1.8)% leaching of surface Bi atoms and a transient dark transition state, which endows the activated T-BWO with exceptional electrochromic performance: an ultralow working voltage window of -0.6/0.3 V, ultrafast coloration/bleaching times of (0.81 ± 0.06)/(0.55 ± 0.04) s, a high coloration efficiency of (148.3 ± 7.8) cm2 C-1, and reasonably fast self-bleaching under open-circuit conditions. The assembled T-BWO-based self-bleaching ECD delivers a moderate optical modulation (ΔR) of (37.8 ± 1.7)% and excellent cycling stability (86% performance retention after 900 cycles). This work not only introduces a novel high-performance inorganic electrochromic material but also provides a new design paradigm for functional ECDs toward practical automotive antiglare applications.