Rb‐Doped Cs₃Cu₂I₅ Perovskite Nanocrystals as Paper‐Based Scintillator Film for High‐Resolution X‐Ray Imaging

Abstract X‐ray detection is a crucial component of digital imaging technology, employed across various fields, from medical diagnostics to security inspections. Traditional scintillators are limited in complex preparation processes, inherent toxicity, and high cost. Copper‐based all‐inorganic halide perovskites have garnered significant attention for their environmental sustainability and zero self‐absorption. In this study, Rubidium (Rb)‐doped Cs 3 Cu 2 I 5 (Cs 3 Cu 2 I 5 :Rb) nanocrystals (NCs) are successfully doped with controllable amount of Rb ions. Experimental data supported by density functional theory (DFT) calculations indicates that Rb leads to densifying the crystal structure, enhances exciton‐photon coupling strength, and increases the probability of radiative recombination. In addition, Rb doping further reduces non‐radiative recombination. Finally, a high photoluminescence quantum yield of 96% is achieved. Furthermore, the synthesized Cs 3 Cu 2 I 5 : Rb NCs are uniformly deposited on cellulose paper to form a scintillator film characterized by high transmittance and high flexibility. This film demonstrates high spatial resolution (14 lp mm −1 ), making it suitable for non‐planar objects X‐ray imaging with minimal image distortion, diminishing blurry imaging. Moreover, this method is universal in Cs 3 Cu 2 X 5 (X = Cl, Br). This work paves the way for the development of non‐toxic, cheap, high‐performance X‐ray imaging devices and demonstrates the practical application of flexible scintillators in X‐ray imaging devices.