Structural Design for W18O49: Ordered‐Disordered Heterojunction Interface Induced Rapid High‐Contrast Photochromism and Customizable Self‐Bleaching Rate

Abstract The applications of tungsten oxide‐based photochromic materials are constrained by their slow photochromic speed, insufficient photochromic contrast, and long self‐bleaching time. The underlying causes of these limitations are not well understood, and the methodology for simultaneously improving these aspects remains to be explored. Herein, an all‐inorganic ordered‐disordered heterojunction interface is presented with high local structural evolution activity, consisting lattice‐disordered W 18 O 49 functionalized with crystalline N‐doped TiO 2 (TiO 2 :N@W 18 O 49 ‐a). This configuration enables over 80% photochromic contrast within 5 s under UV irradiation and complete self‐bleach within 90 s. In situ irradiation (ISI)–electron paramagnetic resonance and ISI–X‐ray photoelectron spectroscopy combined with DFT calculations reveal that this interface induces the localization of photogenerated electrons and promotes the formation of a unique color center configuration (Ti‐O vac ‐W), significantly enhancing both the photochromic speed and the photochromic contrast. Furthermore, this ordered‐disordered interface configuration upshifts the d‐band center of W, facilitating the adsorption of O 2 and thereby ensuring a highly customizable self‐bleaching rate. These advantages establish a foundation for advanced optical applications, and the potential applications of TiO 2 :N@W 18 O 49 ‐a in photochromic smart windows, information encryption, and information storage are demonstrated. This study offers a viable approach for investigating the structure‐performance relationship of inorganic photochromic materials.