Surface Engineering of Cesium Lead Halide Perovskite Nanocrystals for Enhanced Air Stability

Abstract

Cesium lead halide perovskite nanocrystals (CsPbX3 NCs where X is Cl, Br, and I) have become of great interest to numerous researchers because CsPbX3 NCs exhibit highly bright photoluminescence (PL), very narrow full width at half maxima (FWHM) of PL spectra. Also, recently demonstrated soft and dynamic nature of crystal domain in CsPbX3 NCs triggered fundamental interests. However, very unfortunately, it has been known that CsPbX3 NCs are too much unstable under air environment. For instance, PL quantum yield shows drastic drop when the NCs are stored in air conditions. Also, NCs fuse together along [110] crystal direction which finally results in degradation of their initial properties. Therefore, preventing degradation of CsPbX3 NCs in air is the most crucial issue for wider deployment of CsPbX3 NCs. Here, we report surface ligand transition from anionic oleate ligands to cationic oleylammonium ligand on the surface of CsPbX3 NCs. Addition of ZnX2 enables such surface ligand transition of NCs. Furthermore, exposure of fusion-vulnerable (110) facets is markedly inhibited when the surface is terminated with cationic oleylammonium ligands, possibly due to significant difference in formation energy of (100) and (110) facets.