Multimode Long‐Persistent Luminescence and Photochromism From Lead‐Doped CsCdCl 3 Metal Halide Toward Advanced Multiple Anti‐Counterfeiting and Information Storage

Abstract Doping in single‐component metal halide perovskites to adjust defect levels plays a crucial role in self‐trapped exciton (STE) emission, which is critical for tunable multi‐mode luminescence and photochromism (PC). The introduction of cations (Pb 2+ ) into the hexagonal CsCdCl 3 perovskite results in the disruption of the local symmetry of the matrix framework, establishing new trap states and trap centers, which in turn facilitate the creation of multimode persistent luminescence (PersL) materials. Temperature‐dependent fluorescence and thermoluminescence (TL) spectra reveal that Pb 2+ influences the redistribution of defects, providing new emission pathways and enabling efficient tuning of the room‐temperature emission. In addition, chlorine vacancies (V Cl ) in CsCdCl 3 :Pb facilitates the capture of electrons to form F‐centers, resulting in remarkable PC. First‐principles theory simulations demonstrate the introduction of Pb 2+ ions alter the original energy band structure and charge distribution, confirming their tendency to induce defect formation at different symmetry sites. This effective method of modifying the optical properties of CsCdCl 3 microcrystals through Pb 2+ doping integrates multimode tunable UV/X‐ray induced PersL and rewritable PC, offering promising material candidates for more reliable and efficient anti‐counterfeiting and information storage applications.