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

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 CsCdCl₃:Pb perovskite, which integrates blue emission, persistent luminescence, and photochromic behavior into four stimulus response modes, enabling the multi-level information encryption. Notably, CsCdCl₃: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 Pb²⁺ 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.