Surface Passivated Perovskite Single Crystals for X-ray Detectors with High Sensitivity

Perovskite single crystal-based self-powered direct X-ray detectors demonstrate promising performances that rival those of commercial technologies in terms of sensitivity and detection limit. However, surface defects, particularly those induced via post-polishing, detrimentally limit the performance of direct X-ray detectors. In this study, we synthesized perovskite single crystal with composition of $\mathrm{FA}_{0.85} \mathrm{MA}_{0.1} \mathrm{Cs}_{0.05} \mathrm{~Pb}\left(\mathrm{I}_{0.85} \mathrm{Br}_{0.15}\right)_{3}$ and implemented a chemical passivation approach to mitigate defects and improved detector performances. We employed a double-side passivation strategy, wherein we deposited a reactive organic salt of phenethylammonium iodide. This salt exhibits reactivity specifically towards the defective perovskite sites, facilitating the formation of lower-dimensional perovskite layers on both the bottom and top surfaces of the crystal. Chemical passivation leads to a significant reduction in defects, resulting in low dark current with high sensitivity of $3.7 \times 10^{3} \mu \mathrm{C} / \mathrm{Gy} \mathrm{cm}^{2}$ to X-ray responses in the X-ray detector. The detector shows an indicative response for single-photon gamma-ray detection. These findings highlight the practical applications of chemically passivating defects in perovskite single crystals for high performance $\mathrm{X} / \gamma$-ray detectors.