Large‐Area X‐Ray Scintillator Screen Based on Cesium Hafnium Chloride Microcrystals Films with High Sensitivity and Stability

Abstract Lead‐halide perovskites have received extensive attention in X‐ray imaging applications recently. However, their poor stability, lead toxicity, and strong light self‐absorption seriously limit the commercial development. Here, we report a vacancy‐ordered Cs 2 HfCl 6 double perovskite for scintillators applications. The Cs 2 HfCl 6 microcrystals (MCs) are characterized by broadband blue emission with a large Stokes shift. Joined experimental‐theoretical characterizations reveal the highly localized charge distribution in Cs 2 HfCl 6 and structural distortion of [HfCl 6 ] 2− octahedron in the excited state favor the formation of self‐trapped excitons (STEs), which contribute to the broadband emission. Benefiting from the radioluminescence of STEs with negligible self‐absorption, the light yield of Cs 2 HfCl 6 scintillator reaches 21700 photons/MeV, and the detection limit is 55 nGy air s −1 . Additionally, the Cs 2 HfCl 6 scintillator exhibits extremely low hygroscopicity and good resistance to X‐ray irradiation. Further, a large‐area scintillator screen (20×20 cm 2 ) is fabricated by combining scrape‐coating and soft‐pressing techniques, showing a spatial resolution of 11.2 lp mm −1 . Given the high spatial resolution and fast light decay of this scintillator screen, static X‐ray imaging of bulky objects is realized, and dynamic X‐ray imaging of a rotating chopping fan is demonstrated without ghosting effects. These results demonstrate the great commercial promise of Cs 2 HfCl 6 scintillation screens for indirect X‐ray detection.