X‐Ray‐Activated Long Afterglow Double‐Perovskite Scintillator for Detection and Extension Imaging

X‐ray flat‐panel detectors are widely used for nondestructive detection of internal information in medical radiography and industrial applications. However, a persisting challenge is the application of radiography on highly curved 3D objects to realize flexibility and information storage for the fabrication of flexible large‐area X‐ray detectors. This study demonstrates a halide‐based double perovskite Cs2Na0.9Ag0.1LuCl6:Dy3+ by a hydrothermal reaction. The as‐prepared crystals exhibit afterglow features through a co‐doping strategy of Dy3+ and Ag+ ions. The double perovskite material with doping modification exhibits excellent scintillation properties with high sensitivity, low detection limit, and high radiation stability. In addition, flexible scintillator detectors are fabricated with an area of 8.0 × 6.0 cm2 by the blade‐coating strategy, which has a high spatial resolution of 11.2 lp mm−1@MTF = 0.2. Based on the long afterglow properties, the Cs2Na0.9Ag0.1LuCl6:Dy3+ flexible film exhibits thermoluminescence after turning off the X‐ray, thereby having strong potential for X‐ray imaging of nonflat and irregular objects. A new lanthanide‐doped double perovskite scintillation material Cs2NaLuCl6:Dy3+ is proposed with bright yellow luminescence. By a strategy of co‐doping with Ag+, Cs2Na0.9Ag0.1LuCl6:Dy3+ is prepared, which exhibits great scintillation characteristics and long afterglow properties, thus enabling X‐ray extension imaging of nonplanar objects and situations that cannot be imaged in real time.