Super Persistent Luminescence and Photochromism in Cr ³⁺ ‐Doped Pyroxene for Multimodal Applications

ABSTRACT Conventional photoluminescent materials are limited by their single optical response, constraining their use in information storage and anti‐counterfeiting. Emerging strategies, therefore, are focused on multifunctional materials with multimodal, dynamically tunable optical behaviors to achieve higher storage capacity and security. Herein, a pyroxene‐type phosphor Ca(Zn,Mg)Ge 2 O 6 :Cr 3+ integrating both persistent luminescence (PersL) and photochromism has been developed. Under ultraviolet irradiation, the material exhibits a broad near‐infrared persistent emission spanning 700–1300 nm, accompanied by a distinct color change from white (gray) to gray‐pink. By combining bandgap engineering with crystallographic site regulation, the trap depth can be continuously tuned, thereby extending the afterglow lifetime from 20 to over 200 h. The optimized phosphor can be effectively recharged under sunlight, while bandgap engineering further enhances its UV‐induced photochromism behavior. Compared with CaZnGe 2 O 6 :Cr 3+ , CaZn 0.65 Mg 0.45 Ge 2 O 6 :Cr 3+ is characterized by a remarkable 41.7% increase in the reflectance difference (∆R) at 466 nm, together with improved color retention stability. By synergistically coupling PersL with photochromism functionality, the optimized material opens new avenues for multimodal anti‐counterfeiting applications.