Epitaxial Engineering of FAPbBr₃/FAPbBr_3-xCl_x Heterojunctions for Sensitive X-ray and α-Particle Detection

Halide perovskite crystals have attracted extensive research in the field of radiation detection, thanks to their superior carrier transport abilities and facile solution preparation methods. However, dark current instability is common in perovskite single-crystal devices, especially under high bias voltages. Herein, we achieve the modulation of surface defects by epitaxial growth to obtain heterogeneous crystals with high crystalline quality, developing FAPbBr₃/FAPbBr_3-xCl_x heterojunctions to address severely increased dark current. The FAPbBr₃/FAPbBr_2.7Cl_0.3 heterojunction exhibits reduced trap-state density and a significant built-in potential difference. Based on the effective utilization of the dark current cutoff effect of the heterojunctions, a dark current of 0.83 μA·cm^-2 is realized for the FAPbBr₃/FAPbBr_2.7Cl_0.3 detector, which is 7.5% of that based on an intrinsic FAPbBr₃ single crystal. Thus, an optimal sensitivity of 33612 μC·Gy_air^-1·cm^-2 for Au/FAPbBr₃/FAPbBr_2.7Cl_0.3/Au detector was achieved, at a bias of −250 V. Simultaneously, an energy resolution of 15.2% for ²⁴¹Am @ 5.49 MeV α-particle-induced pulse height spectra was recognized. Our work not only establishes a new benchmark for FAPbBr₃-based perovskite performance but also presents a pragmatic strategy to lower the harmful dark current in three-dimensional halide perovskite single crystals.