Extrinsic Self-Trapped-Exciton Emission in Cs₅Cu₃Cl₆I₂ for Efficient X-Ray Scintillation

Efficient and stable scintillators play a crucial role in X-ray detection applications. To enhance the luminescence efficiency under X-ray excitation, the incorporation of multiple emission centers into scintillators is widely explored. Here, it is found that the cesium copper halide Cs₅Cu₃Cl₆I₂ exhibits dual emission centers, enabling high-performance scintillators with an X-ray light yield of 49000 photon MeV⁻¹ and a low detection limit of 4 nGy s⁻¹. The emissions of Cs₅Cu₃Cl₆I₂ are from intrinsic self-trapped exciton (STE) and Frenkel defect-assisted STE. High-energy X-rays can induce an increased fraction of Frenkel defect-assisted STEs, which can serve as an effective scintillation channel. Furthermore, large-area flexible scintillators with a high resolution of 18 lp mm⁻¹ are developed, making them suitable for X-ray imaging applications. These findings offer promising insights for developing more efficient scintillators.