Unveiling the doping effect of mixed-halide CsPb(Br_1−<i>n</i>X_<i>n</i>)₃ (X = I, Cl) single crystals toward high-sensitivity radiation detection

Metal halide perovskites are promising materials for next-generation X-ray detectors. Among these materials, CsPbBr₃ single crystals (SCs) exhibit high environmental stability, low defect density and high X-ray absorption coefficient, demonstrating excellent X-ray detection performance. However, ion migration in CsPbBr₃ induces dark current drift, leading to a decrease in photocurrent and an increase in detection limit. Doping CsPbBr₃ SCs with mixed halides has emerged as an effective strategy to suppress ion migration, increase resistivity and improve detection sensitivity. In this study, we synthesized lightly doped mixed-halide perovskite CsPb(Br_1-<i>n</i>X_<i>n</i>)₃ (X = Cl, I) SCs with high crystallinity and compositional uniformity using the inverse temperature crystallization method and systematically studied hole and electron transport properties. Our findings indicate that the dark current primarily arises from hole current driven by ion migration associated with halide vacancies. Both chlorine doping and iodine doping suppress ion migration, with iodine doping exhibiting the best inhibiting effect. With low work function contacts, electron dark current is substantially reduced due to the elimination of hole contributions, and the dark current drift is effectively suppressed. Electron transport dynamics were further explored through α-particle spectroscopy. Analysis of α-particle spectra and carrier transit times revealed that chlorine doping enhances the <i>μ</i>-<i>τ</i> product and charge collection efficiency, whereas light iodine doping results in reduced <i>μ</i>-<i>τ</i> product and slower charge transport. Overall, halide doping combined with contact engineering demonstrates that mixed-halide perovskites hold significant promise for developing high-performance X-ray detectors.