Mg(II)-Doped Perovskite-like Cs3Cu2I5 Single Crystals with High Quantum Yield for Efficient X-ray Detection

Cs3Cu2I5 halide perovskites doped with luminescence activators have unique optical and electronic properties; however, they tend to combine with slow scintillation decay, which leads to ghosting or blurriness during X-ray imaging. In this study, we produced magnesium (Mg2+)-doped Cs3Cu2I5 single crystals (SCs) with blue emission at 440 nm, and the photoluminescence quantum yields ranged from 72.4 to 81.7%. Moreover, enhanced radioluminescence (RL) intensity and light output were achieved without deteriorating scintillation decay compared to those of pure Cs3Cu2I5 SCs. Mg doping can strengthen electron–phonon coupling, and the emission (2.15 eV) at a low temperature (80–290 K) showed the presence of additional carrier capture channels of Mg-related defect levels in the band gap, which can help reduce the probability of nonradiative recombination. Therefore, flexible X-ray scintillator films with excellent hydrophobicity were fabricated using Mg2+-doped Cs3Cu2I5 SC powders, and their spatial resolution (2.5 Lp/mm) met the resolution requirements of commercial spiral computed tomography. This study found an effective strategy for enhancing the self-trapped exciton emission of metal copper-based halide scintillators and highlighted their applicability in low-dose flexible X-ray detection and imaging.