Suppression of Defect Formation in CsPbBr ₃ Nanocrystals via Stoichiometry Regulation for Sensitive and Stable Nanocomposite X–Ray Detectors

Perovskite nanocrystals (PNCs) have emerged as promising candidates for X‐ray detection due to their large X‐ray stopping power and their presynthesized crystalline nature, which enables high‐quality thick‐film deposition via a scalable spray coating process. However, the inherent high defect density at the surface of PNCs significantly hampers the charge collection efficiency and overall stability of X‐ray detectors. In this study, the Cs/Pb precursor ratio is identified as a critical factor in mitigating defect formation in CsPbBr 3 PNCs. By introducing a moderate Cs‐deficient stoichiometry, both defect density and self‐doping within the PNCs are effectively reduced. Additionally, PNCs are incorporated into organic bulk‐heterojunctions to fabricate nanocomposite X‐ray detectors, showing that this stoichiometry regulation not only enhances the detectors’ sensitivity but also decreases the dark current and significantly improves their environmental stability. These advancements hold substantial potential for high‐performance flat‐panel X‐ray imaging applications in the future.