Postsynthesis Transformation of Insulating Cs₄PbBr₆ Nanocrystals into Bright Perovskite CsPbBr₃ through Physical and Chemical Extraction of CsBr

High Resolution Image Download MS PowerPoint Slide Perovskite-related Cs 4 PbBr 6 nanocrystals present a “zero-dimensional” crystalline structure where adjacent [PbBr 6 ] 4– octahedra do not share any corners. We show in this work that these nanocrystals can be converted into “three-dimensional” CsPbBr 3 perovskites by extraction of CsBr. This conversion drastically changes the optoelectronic properties of the nanocrystals that become highly photoluminescent. The extraction of CsBr can be achieved either by thermal annealing (physical approach) or by chemical reaction with Prussian Blue (chemical approach). The former approach can be simply carried out on a dried film without addition of any chemicals but does not yield a full transformation. Instead, reaction with Prussian Blue in solution achieves a full transformation into the perovskite phase. This transformation was also verified on the iodide counterpart (Cs 4 PbI 6 ).