Enhanced luminescence and dispersion stability of lead halide perovskite nanocrystals by surface modification via O/W emulsion

Metal halide perovskite nanocrystals (NCs) attract tremendous research attentions as next-generation functional materials due to their excellent photophysical nature. A common disadvantage of perovskite NCs is very poor stability and dispersibility in polar solvents. Then, we encapsulate CsPbBr3 NCs into an oil-in-water (O/W) emulsion formed with sodium bis(2-ethylhexyl)sulfosuccinate (AOT) to improve their dispersion property and chemical stability. X-ray diffraction and X-ray photoemission spectroscopy indicate that the non-luminescent Cs4PbBr6 NC precursor converted to luminescent CsPbBr3 NCs in the O/W emulsion process, as excess CsBr dissociated at emulsion interfaces. CsPbBr3 NCs encapsulated with an AOT-based emulsion shell (AOT-modified CsPbBr3 NCs) were obtained after freeze-drying the O/W emulsion, exhibiting good dispersibility in hydrophilic polar solvents such as alcohols and water. The photoluminescence intensity of AOT-modified CsPbBr3 NCs remained 40-56% even after dispersion in water for 180 min, while unmodified ones rapidly degraded within 30 min. These results suggest that the interfacial molecular order of the O/W emulsion should be condensed on the surfaces of CsPbBr3 NCs and enhance their affinity and stability to polar solvents. The present findings provide a facile surface modification approach to attain perovskite and related halide compounds NCs applicable to polar solvents or water environments.