Efficient Ligand Passivation Enables Ultrastable CsPbX₃ Perovskite Nanocrystals in Fully Alcohol Environments

Abstract Halide perovskite nanocrystals (PNCs) have demonstrated their wide potential to fabricate efficient optoelectronic devices and to prepare promising photocatalysts for solar‐driven photo(electro)chemical reactions. However, their use in most of the practical applications is limited due to the instability of PNCs in polar environments. Here, the preparation of non‐encapsulated CsPbX 3 nanocrystals dispersed in fully alcohol environments, with outstanding stability through surface defect passivation strategy is reported. By using didodecyldimethylammonium bromide (DDAB) during material post‐treatment, highly luminescent CsPbBr 3 PNCs with remarkable stability in methanol/butanol medium up to 7 months with near‐unity photoluminescence quantum yield are achieved. This approach is extrapolated to stabilize iodine‐based CsPbBr 3‐ x I x and CsPbI 3 PNCs, showing an improvement of their photoluminescence features and stability in these high polar alcohols up to 6 h. DDAB mediates the defect suppression through ligand exchange and avoids the full permeation of alcohol to be in contact with the PNCs. In this context, DDAB induces ionization of alcohol molecules to strengthen the surface passivation. The findings open the door to the development of long‐term stable CsPbX 3 PNCs with high optical performance to be used in polar environments.