Nonstoichiometry Promoted Solventless Recrystallization of a Thick and Compact CsPbBr3 Film for Real‐Time Dynamic X‐Ray Imaging

Abstract Inorganic CsPbBr 3 perovskite emerges as a promising material for the development of next‐generation X‐ray detectors. However, the formation of a high‐quality thick film of CsPbBr 3 has been challenging due to the low solubility of its precursor and its high melting point. To address this limitation, a nonstoichiometry approach is taken that allows lower‐temperature crystallization of the target perovskite under the solventless condition. This approach capitalizes on the presence of excess volatile PbBr 2 within the CsPbBr 3 film, which induces melting point depression and promotes recrystallization of CsPbBr 3 at a temperature much lower than its melting point concomitant with the escape of PbBr 2 . Consequently, thick and compact films of CsPbBr 3 are formed with grains ten times larger than those in the pristine films. The resulting X‐ray detector exhibits a remarkable sensitivity of 4.2 × 10 4 µC Gy air −1 cm −2 and a low detection limit of 136 nGy air s −1 , along with exceptional operational stability. Notably, the CsPbBr 3 ‐based flat‐panel detector achieves a high resolution of 0.65 lp pix −1 and the first demonstration of real‐time dynamic X‐ray imaging for perovskite‐based devices.