Sensitive and Fast X‐Ray Scintillation with Perovskite‐Inspired Cerium Halide Nanocrystals

Abstract Real‐time, high‐precision X‐ray imaging is of critical importance in a wide range of applications, from medical diagnostics to security screening. While lanthanide luminescent materials are among the most commonly used scintillators, achieving a combination of large‐area scalability, rapid response, and optimal performance remains challenging. Herein, a perovskite‐inspired cerium halide nanocrystal scintillator is presented with a remarkable photoluminescence quantum yield approaching unity and a fast radiative recombination rate of ≈29 ns. By leveraging these promising characteristics, large‐area X‐ray imaging is demonstrated with a spatial resolution of 12.21 lp mm −1 and an ultra‐low detection limit of 11.2 nGy s −1 , alongside applications in dynamic imaging. Based on these paternal nanocrystals, the versatile spectral tunability through halide alloying and cation doping is further explored, offering a promising platform for future chemical and structural design toward advanced scintillations and other down‐conversion applications.