Controllable synthesis and enhanced photochromic performance of Er-doped WO₃ nano neural network-like structures

Tungsten trioxide (WO₃) is a well-known photochromic material that undergoes a reversible color change under light irradiation, making it promising for applications in smart windows, optical storage, and sensing devices. This study presents the successful synthesis of a uniform and morphology-controlled WO₃ neural network-like structure by tuning the hydrothermal reaction temperature and hydrochloric acid concentration. Furthermore, the photochromic response time of the as-prepared WO₃ particles was systematically investigated, and the optimal sample exhibiting the fastest response was identified. To significantly enhance the photochromic performance, erbium (Er), a rare earth element, was introduced as a dopant. According to the results, Er doping significantly prolonged the photochromic response time of WO₃. The incorporation of Er led to a noticeable narrowing of the optical bandgap, as confirmed by UV-vis absorption and Tauc analysis. The Er_0.03W_0.97O₃ composition demonstrated superior performance compared to the other analyzed samples, indicating that the incorporation of rare earth elements can effectively regulate the photochromic behavior of WO₃ and provide a new pathway for tailoring its optical properties.