Transformation of Metal Halides to Facet-Modulated Lead Halide Perovskite Platelet Nanostructures on A-Site Cs-Sublattice Platform.

The conversion of metal halides to lead halide perovskites with B-site metal ion diffusion has remained a convenient approach for obtaining shape-modulated perovskite nanocrystals. These transformations are typically observed for materials having a common A-site Cs-sublattice platform. However, due to the fast reactions, trapping the interconversion process has been difficult. In an exploration of the tetragonal phase of CsCdBr platelets as the parent material, herein, a slower diffusion of Pb(II) leading to facet-modulated CsPbBr platelets is reported. This was expected due to the presence of Cd(II) halide octahedra along with Cd(II) halide tetrahedra in the parent material. This helped in microscopically monitoring their phase transformation via an epitaxially related core/shell intermediate heterostructure. The transformation was also derived and predicted by density functional theory calculations. Further, when the reaction chemistry was tuned, core/shell platelets were transformed to different facet-modulated and hollow CsPbBr platelet nanostructures. These platelets having different facets were also explored for catalytic CO reduction, and their catalytic rates were compared.