Single‐Component White Light and X‐ray Sensing: Lead‐Free K/Sb:Cs ₂ ScCl ₅ ·H ₂ O Crystals for Dual‐Functional Optoelectronic Applications

ABSTRACT Low‐dimensional lead‐free metal halide perovskites hold immense potential for optoelectronic applications, yet achieving single‐component materials that simultaneously enable tunable broadband emission and high‐performance X‐ray detection remains a critical challenge. Therefore, we developed a novel doping strategy for engineering dual‐mode luminescence and detection functionalities in non‐toxic perovskite systems. Here, K/Sb co‐doped Cs 2 ScCl 5 ·H 2 O crystals were synthesized via a hydrothermal method, demonstrating two synergistic innovations. First, a dual self‐trapped exciton (STE) emission mechanism was established that combines intrinsic lattice distortion‐induced emission (588/595 nm) and Sb‐mediated defect‐state near‐infrared transitions (718 nm), enabling excitation‐independent broadband luminescence. Furthermore, we accomplished concurrent warm white‐light emission (CIE: 0.477, 0.471) and ultrasensitive X‐ray detection (detection limit: 40.595 nGy·s −1 ; resolution: 15.9 lp/mm) based on K/Sb co‐doped Cs 2 ScCl 5 ·H 2 O crystals. This research provides a systematic guideline for designing perovskite crystals tailored for both WLEDs and high‐performance X‐ray detectors.