Surface passivated 3D halide perovskite single crystal by 2D perovskite towards high performance soft X-ray detection and gamma-ray spectrum

Abstract

Metal halide perovskite single crystals exhibit a significantly lower defect density and superior charge transport properties compared to polycrystalline materials, demonstrating outstanding performance in X-ray and γ-ray detection. However, the surface defect density of single crystals is substantially higher than that of the bulk, which severely limits the development of perovskite single crystal devices. In this study, we explore a surface passivation strategy for single crystals by constructing a 2D/3D heterojunction on the surface of 3D perovskite single crystals. Specifically, we directly grew a layer of ThMA₂PbBr₄ with nanometer-scale thickness on the surface of FAPbBr₃ single crystals, which effectively suppressed the formation of secondary phases at the 2D/3D interface and passivated the surface defects of the 3D perovskite single crystals. As a result, the surface trap density was reduced by more than an order of magnitude, and the carrier diffusion coefficient was enhanced by over twofold. When applied to soft X-ray detection, the treated FAPbBr₃ single crystals exhibited a response time that was reduced by two orders of magnitude compared to untreated crystals. The sensitivity is comparable to the best performance of planar structured (M−S−M) soft X-ray detectors. In devices based on the Bi/FAPbBr₃/Au structure, the dark current density of the treated single crystal device was reduced by an order of magnitude, and an energy resolution of 6.3 % was achieved for 662 keV γ-rays, which was not attainable before treatment.