Synergistic Compatibilization of CsPbBr ₃ Perovskites and HfO ₂ Nanocrystals for Hybrid Sensitized Nanoscintillators

Abstract Lead halide perovskite nanocrystals (NCs), such as CsPbBr 3 , are promising candidates for next‐generation scintillators due to their ultrafast radiative kinetics and high emission efficiency. However, their integration in composite scintillators is limited by poor compatibility with high‐Z sensitizers, reabsorption losses at high loading, and low radiation stopping power due to their nanoscale dimensions. Here, a robust strategy is demonstrated to hybridize CsPbBr 3 NCs with hafnium oxide (HfO 2 ) nanoparticles (NPs) as transparent, high‐Z electromagnetic sensitizers. Surface oxygen dangling bonds on HfO 2 NPs are identified as the main source of perovskite degradation and it is shown that a PbBr 2 pre‐treatment effectively passivates these sites. This enables stable NC–NP hybrids, preserving optical quality and scintillation properties. Co‐synthesis in the presence of treated HfO 2 NPs suppresses NC degradation and enhances both photoluminescence efficiency and thermal robustness. The hybrids can be embedded in polymer nanocomposites via thermal radical polymerization, a process typically detrimental to perovskites. Under X‐ray excitation, HfO 2 NPs significantly enhance radioluminescence intensity without compromising the ultrafast response of CsPbBr 3 NCs, confirming efficient electromagnetic sensitization via electron cascade. This work offers a viable pathway for designing hybrid nanoscintillators with enhanced stopping power and stable optical performance for practical radiation detection technologies.