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.