Electron Trap Induced Multimodal Luminescence and Photochromism for Optical Thermometry and Information Encryption

ABSTRACT Achieving multimodal response to various stimuli in a single luminescent material is crucial for advanced anti‐counterfeiting and encryption. However, the simultaneous realization of multimodal luminescence and photochromism (PC) properties in one matrix remains a significant challenge. Here, a multimodal luminescent ceramic phosphor was developed via Bi 3+ doping into inverse spinel structure MgGa 2 O 4 lattice, which exhibits response upon ultraviolet (UV), near‐infrared (NIR), X‐ray, and thermal stimuli, specifically showing temperature‐dependent multicolor luminescence (blue‐white‐red), high thermal stability of 397 nm emission (90%@473 K), and rapid PC properties (within 1 s). Through experimental analysis and density functional theory (DFT) calculations reveals that the multi‐color luminescence is mainly associated with interstitial oxygen and antisite defects, whereas PC is related to color centers formed by oxygen vacancies; anti‐thermal quenching originates from the compensation of non‐radiative luminescence by electrons in trap levels at high temperatures. Based on these findings, precise control over the optical properties of the MgGa 2 O 4 :Bi 3+ ceramic phosphors are achieved for applications such as temperature monitoring and information encryption. This work provides valuable insights for the design of multimodal stimuli‐responsive systems.