Although metal halide perovskites have advanced rapidly in photoelectrical detection, studies on perovskite-based photon-counting detector remain scarce. This study reports an efficient perovskite photon-counting detector achieved through defect passivation of the perovskite photosensitive layer. Urea, a Lewis base, was introduced as an additive during the two-step fabrication of MAPbI₃ films, forming a complex (MAI·PbI₂·O=C(NH₂)₂, where MAI = methylammonium iodide) that slowed the reaction rate and promoted complete reaction between MAI and PbI₂. Compared to conventional perovskite films, the optimized MAPbI₃ film exhibits enhanced crystallinity, with enlarged grain size from 254.8 to 908.1 nm, and reduced defect density from 9.08 × 10¹⁵ to 3.89 × 10¹⁵ cm⁻³. The resulting MAPbI₃ photodiode detector demonstrates satisfactory performance, achieving a responsivity of 0.4 A/W and a sensitivity of 2.39 × 10¹³ Jones under 17.02 μW/cm² illumination. Furthermore, a photon-counting system integrated with the MAPbI₃ photodetector was able to detect low light levels down to 2.01 × 10³ photons per mm², with a photoresponse three times higher than that of silicon-based photon-counting detector.

Inorganic perovskite wafers with good stability and adjustable sizes are promising in X-ray detection but the high synthetic temperature is a hindrance. Herein, dimethyl sulfoxide (DMSO) is used to prepare the CsPbBr₃ micro-bricks powder at room temperature. The CsPbBr₃ powder has a cubic shape with few crystal defects, small charge trap density, and high crystallinity. A trace amount of DMSO attaches to the surface of the CsPbBr₃ micro-bricks via Pb–O bonding, forming the CsPbBr₃-DMSO adduct. During hot isostatic processing, the released DMSO vapor merges the CsPbBr₃ micro-bricks, producing a compact and dense CsPbBr₃ wafer with minimized grain boundaries and excellent charge transport properties. The CsPbBr₃ wafer shows a large mobility-lifetime (μτ) product of 5.16 × 10^-4 cm²·V⁻¹, high sensitivity of 14,430 µC·Gy_air⁻¹·cm⁻², low detection limit of 564 nGy_air·s⁻¹, as well as robust stability in X-ray detection. The results reveal a novel strategy with immense practical potential pertaining to high-contrast X-ray detection.