Ultra‐Stable Metal Halide Perovskite Nanocrystals with Controllable Dimension by Block Copolymer Micelle Templates

Abstract Metal halide perovskite nanocrystals (PNCs) have attracted significant research interest owing to their exceptional photovoltaic properties and their potential applications in photovoltaics and light‐emitting devices. However, stabilizing individual PNCs while maintaining their intrinsic properties remains a great challenge. In this study, a facile yet robust approach is introduced by utilizing polystyrene‐ block ‐poly(4‐vinyl pyridine) (PS‐ b ‐P4VP) block copolymer micelles as templates to precisely control the formation, size, and stability of CsPbBr 3 PNCs. Interestingly, the reaction kinetics of PNC precursors in the micelles can be modulated by stacking of polymer chains via crosslinking of P4VP cores or collapsing of micelle templates, enabling facile control over the geometry of PNCs inside the micelles. By tuning the molecular weight of P4VP, precise size control of the CsPbBr 3 PNCs can be achieved. Most importantly, the hydrophobic PS shell enhances the stability of PNCs against moisture and polar solvents (e.g., methanol, ethanol, dichloromethane, etc.) without interference in ion exchange processes. The approach enables the in situ growth of monodisperse CsPbBr 3 PNCs, offering a straightforward and scalable method for fabricating highly stable, size‐controlled PNCs suitable for optoelectronic applications.