Improving the Stability of CsPbBr3 Nanocrystals in Ethanol by Capping with PbBr2-Adlayers

All inorganic lead halide perovskite (CsPbX3, X = Cl, Br, and I) nanocrystals (NCs) have been widely investigated and applied in optoelectronic devices because of their excellent photophysical and carrier transport properties. However, poor stability of lead halide perovskite NCs upon exposure to a polar solvent, such as ethanol, greatly limits their practical application. In this work, we have developed an easy way to encapsulate CsPbBr3 NCs with PbBr2-adlayers by employing didodecyl dimethyl ammonium bromide (DDAB) molecules as the only bromine source and capping ligands. XPS analyses demonstrate that PbBr2-adlayers can be formed on CsPbBr3 NCs only by carefully controlling the precursor composition. The successful encapsulation of PbBr2-adlayers enables dense packing of DDA(+) ligands on the NC surface, which greatly enhances their stability in ethanol. These PbBr2-adlayer-encapsulated CsPbBr3 NCs retained similar to 95% of their initial photoluminescence intensity after dispersing in the mixture of ethanol and n-hexane for 6 h. Such excellent ethanol-resistant behavior may be helpful for further processing and applications of CsPbBr3 NCs.