Chemically Sculpturing\nthe Facets of CsPbBr₃ Perovskite Platelet Nanocrystals

Abstract

The facet chemistry of lead halide perovskite nanocrystals\nis critically\nimportant for determining their shape and interface ligand binding.\nIn colloidal nanocrystals, these are mostly controlled by adopting\nspecific synthetic strategies with a selection of the appropriate\nreactants. However, using selected ligands, the surface of preformed\nnanocrystals can be reconstructed without altering the crystal phase\nand lattice structure of their core. This has been shown here for\nhexagonal-shaped orthorhombic CsPbBr₃ platelet nanocrystals.\nWhen oleylammonium bromide was added to these postsynthesized platelets,\nall six edges and two planar facets are transformed from flat to wavy\nstructures. With a variation in concentration, the crest-to-crest\ndistance of these wavy platelets are also tuned. These became possible\nbecause of the oleylammonium ions, which changed the {200}, {012}\nand {020} facets of orthorhombic phase of CsPbBr₃ to the\nmore compatible {110} and {002} facets simply by surface atom dissolution.\nThis was also observed for multisegmented platelets having multiple\njunctions and even for platelets having a size of more than 200 nm.\nWhile shape modulations in ionic halide perovskite nanocrystals still\nface synthetic challenges, these results of surface reconstruction\nprovide strong evidence of the possibility of sculpturing surface\nfacets and shape changes in these nanostructures.