Reversible X‐Ray Memory Imaging for Cadmium‐Based Perovskites: Deep Trap‐Driven Radioluminescence Enhancement

ABSTRACT X‐ray imaging has attracted significant attention for information encryption and anti‐counterfeiting. However, ensuring information security under multi‐level encryption scenarios remains challenges. Herein, we have developed a reversible X‐ray memory imaging technique for CsCdCl 3 :Pb perovskite, which integrates blue emission, persistent luminescence, and photochromic behavior into four stimulus response modes, enabling the multi‐level information encryption. Notably, CsCdCl 3 :Pb exhibits photochromic deepening, accompanied by a two‐fold enhancement in radioluminescence (RL) intensity with increasing X‐ray irradiation time. This enhancement originates from the formation of a new deep trap (0.79 eV) that facilitates energy transfer from the color centers to the Pb 2+ emission centers. Importantly, X‐ray memory imaging is attributed to the differences in RL enhancement between extending X‐ray irradiation time and turning on the X‐ray tube after removing capsule, which is demonstrated by cycling tests and stability characterizations under different dose rates. As a result, the RL enhancement and X‐ray memory imaging share common advantages: reversibility, fast response (5 s), rapid erasure capability (450 nm, 10–20 s), fatigue resistance (more than 100 cycles), and long‐term stability (more than half a year). This work presents an effective strategy for designing multi‐mode stimulus response perovskite materials and opens a new avenue for advanced multi‐level information security.