Sequential Phase‐Engineered Afterglow Modulation in Mn‐Doped Cs‐Cd‐Cl Perovskites for X‐ray Time‐Lapse Flexible Imaging

Abstract X‐ray time‐lapse flexible imaging and information retrieval significantly broaden the application scope of X‐ray technologies, while posing new challenges for the design of advanced scintillators. Herein, we report a phase transition–guided strategy for the rational design of Mn‐doped ternary cadmium chlorides long afterglow emitters, wherein crystal growth dynamics are precisely modulated via solubility‐controlled synthesis. By sequentially preparing powders and single crystals of Cs 2 CdCl 4 :Mn, Cs 3 Cd 2 Cl 7 :Mn, and CsCdCl 3 :Mn, we achieve phase‐selective synthesis through fine‐tuning of mixed solvent ratios, establishing a robust framework for phase engineering in the Mn‐doped Cs–Cd–Cl system. Among them, CsCdCl 3 :Mn exhibits the highest trap density, resulting in a pronounced scintillation afterglow. Benefiting from this unique property, a flexible scintillating film fabricated by embedding phosphor powders into a polymer matrix enables high‐resolution time‐lapse X‐ray imaging (13.6 lp mm −1 ), along with thermally stimulated image retrieval after X‐ray exposure. This work not only presents a generalizable approach for phase‐controlled afterglow modulation in Mn‐doped chlorides, but also offers new avenues toward flexible, high‐performance X‐ray scintillators with delayed visualization capabilities.