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.