Enhanced photochromic performance of Zn-doped W18O49-based films for smart windows

Abstract

Tungsten oxides have attracted much attention and research in the field of photochromic smart windows, but their application is limited by their slow light response and poor reversibility. In order to overcome the limitations, Zn²⁺-doped W₁₈O₄₉ nanoparticles were prepared using a facile hydrothermal method and they exhibited good photochromic performance with a quick coloring rate under UV irradiation because more oxygen vacancies in the crystal lattice caused by Zn doping could facilitate the reduction of W⁶⁺ to W⁵⁺, which was confirmed from XRD and XPS results. In addition, the Zn-doped W₁₈O₄₉ nanoparticle-based films showed excellent photochromic properties with a high visible transmittance (T_lum) of 85.33%, a large solar modulation efficiency (ΔT_sol) of 47.18% and a fast photochromic speed (3 min) as well as good cycling stability. These properties are better than those reported in most previous works. Therefore, this work can provide a promising photochromic material with high performance for smart windows.