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

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 (MAPbBr(3)) film on top of bulk mm-sized single crystals. Such MAPbBr(3) crystals with a MAPbBr(3 )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 MAPbBr(3) crystals that show no emission under UV light. Time-resolved photoluminescence and electrical measurements indicate that the MAPbBr(3) film/MAPbBr(3) crystals possess less surface defects compared to the bare MAPbBr(3) crystals. Therefore, X-ray detectors fabricated using the surface-engineered MAPbBr(3) crystals provide an almost 5 times improved sensitivity to X-rays and a more stable baseline drift with respect to the typical MAPbBr(3) crystals.