Surface Engineering of Methylammonium Lead Bromide Perovskite Crystals for Enhanced X-ray Detection

Abstract

The surface quality of lead halide perovskite crystals can extremely influence their optoelectronic properties and device performance. Here, we report a surface engineering crystallization technique in which we in situ grow a polycrystalline methylammonium lead tribromide (MAPbBr₃) film on top of bulk mm-sized single crystals. Such MAPbBr₃ crystals with a MAPbBr₃ passivating film display intense green emission under UV light. X-ray photoelectron spectroscopy demonstrates that these crystals with emissive surfaces are compositionally different from typical MAPbBr₃ crystals that show no emission under UV light. Time-resolved photoluminescence and electrical measurements indicate that the MAPbBr₃ film/MAPbBr₃ crystals possess less surface defects compared to the bare MAPbBr₃ crystals. Therefore, X-ray detectors fabricated using the surface-engineered MAPbBr₃ crystals provide an almost 5 times improved sensitivity to X-rays and a more stable baseline drift with respect to the typical MAPbBr₃ crystals.