Defect Engineering in Cesium Cadmium Perovskites Enables Multi‐Stimuli‐Responsive Luminescence for Temperature‐Resilient X‐Ray Radiography and Mechanosensing

ABSTRACT Halide perovskites have revolutionized optoelectronic technologies, yet their intrinsic defects are viewed as liabilities to be eliminated. Here, we challenge this paradigm by demonstrating that controlled manipulation of defect states in cesium cadmium perovskites transforms these inherent traps into functionally tunable charge carrier reservoirs. Using valence‑engineered doping with Mn 2+ and multivalent ions, we systematically modulate the depth and capacity of carrier traps across 100 to 700 K. Comprehensive thermoluminescence spectroscopy reveals a hierarchical trap landscape, while first‑principles calculations verify the intervalence charge transfer from Mn 2+ to the conduction band. These computational insights, combined with the experimental data, provide electronic‑level validation of the charge trapping and release and offer a mechanistic framework for understanding the origins of trap states in the Mn 2+ ‑doped system. The resulting materials exhibit exceptional temperature resilience and tri‑stimuli‑responsive (optical/thermal/mechanical) luminescence, with 8‑ to 30‑fold enhanced charge storage over commercial benchmarks (BaFBr(I):Eu 2+ and Y 2 O 2 S:Eu 3+ ). Remarkably, mechanical stimulation triggers immediate mechanoluminescence for real‑time force monitoring while simultaneously storing residual charges for delayed thermoluminescent readout. This dual‑mode functionality, enabled by control over trap population dynamics, establishes cesium cadmium halide perovskites as versatile platforms for adaptive X‑ray radiography and wide‑temperature‑range mechanosensing, opening new avenues for smart sensing systems in extreme environments.