Metal Halide Perovskite Enriched with Entropy-Induced Lattice Distortion for Enhanced X-ray Detection

Scintillator-based X-ray imaging technology is widely applied in medical diagnostics and nondestructive detection. Low-dimensional metal halide perovskites (MHPs) offer great potential in scintillation applications due to their flexible crystal structures. However, achieving strongly localized excitonic emission in low-dimensional MHPs remains challenging to further improve the photoemission performance. Herein, we report an entropy-engineering strategy to construct four-element Cs2MCl6 (M = Te4+, Sn4+, Zr4+, and Hf4+) vacancy-ordered double-perovskite scintillators for enhanced X-ray detection, demonstrating an 8-fold enhancement in photoluminescence quantum yield, a 17-fold enhancement in photoluminescence intensity, and a low detection limit of 50.3 nGy s-1. Structural characterizations combined with theoretical calculations reveal that increased configurational entropy induces intense lattice distortion in [MCl6]2- octahedral clusters, increasing exciton transport barriers. Femtosecond transient absorption and temperature-dependent spectroscopic analyses indicate that this four-element Cs2MCl6 shows strong electron-phonon and energy interactions between confined exciton states in isolated [MCl6]2- octahedral structures, thus promoting photoluminescence emission. A flexible scintillation screen containing high-entropy Cs2MCl6 achieves a high resolution of over 20 lp mm-1 for X-ray imaging. This work presents enhanced emission of MHPs by entropy engineering, providing potential implications for radiation detection and other optoelectronic applications.