α-Halo Ketone for Polyhedral Perovskite Nanocrystals: Evolutions, Shape Conversions, Ligand Chemistry, and Self-Assembly

Abstract

Bright lead halide perovskite nanocrystals, which have been extensively studied in the past 5 years, are mostly confined to a six faceted hexahedron (cube/platelet) shape. With variations of ligand, precursor, reaction temperature, and surface modification, their brightness has been enhanced and phase became stable, but ultimate nanocrystals still retained the hexahedron cube or platelet shape in most of the hot injection reactions. In contrast, by exploration of α-halo ketone in amine as a halide precursor, different shaped nanocrystals without compromising the photoluminescence quantum yield (PLQY) are reported. Confining to orthorhombic CsPbBr3, the obtained nanocrystals are stabilized by 12 facets ({200}, {020}, {112}) and led to 12 faceted rhombic dodecahedrons. These facets are absolutely different from six ({110}, {002}) equivalent facets of widely reported orthorhombic cube shaped CsPbBr3 nanocrystals. These also retained the colloidal and phase stability, as well as showed near unity PLQY. With further annealing, these are transformed to 26 faceted rhombicuboctahedrons by dissolving all their vertices. Importantly, these 12 faceted nanocrystals showed wide area self-assembly in most of the reactions. It has also been concluded that primary ammonium ions led to six faceted nanocrystals, but tertiary ammonium ions obtained in this case stabilized different group of facets. While perovskite nanocrystals were broadly confined to only nanocubes, these new nanocrystals with intense emission would certainly provide a new avenue for continuing their further research.

Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals

“…[ 177 ] In this report, a 12 faceted rhombic dodecahedron formed due to the in situ formation of a tertiary ammonium species upon reaction with the α ‐halo ketone, showing a dependence of the polyhedron geometry on ligand concentrations (i.e., tertiary ammonium ions). [ 177 ] Beyond synthesis, these facet‐variable polyhedron LHP NCs have already shown promise in self‐assembly [ 178 ] and photocatalysis. [ 179 ]…”

The making of a reconfigurable semiconductor with a soft ionic lattice

“…morphology, size, facet exposure, and phase or composition have been developed (Fig-ures 2A-2D). 8,9,20 Although the synthetic conditions of halide perovskites resemble those of covalent semiconductor nanocrystals, the studies following the first colloidal synthesis of perovskite nanocrystals reveal the distinct thermodynamic properties of halide perovskites, such as relatively low reaction temperature, easily achieved morphology tunability, and dynamical ligand shells.…”

“…Nanocrystal building blocks and their self-assembly (A-D) Colloidally synthesized cesium-lead-bromide nanocubes, rhombic dodecahedrons, nanowires, and nanoplates, respectively, as nanoscale building blocks. [19][20][21] Copyright 2019 American Chemical Society.…”

Self‐Healing of Crystal Voids in Double Perovskite Nanocrystals Is Related to Surface Passivation

“…[5] The increase in photoluminescence of NCs and efficiency of bulk perovskite solar cells [6][7][8][9][10] are assigned to the diffusion of defects to grain boundaries, accompanied by crystal facet reconstruction at room temperature. [11] Self-healing is the spontaneous ability of a crystal to anneal and recover from structural enable to generate voids and measure diffusive properties with atomic resolution. We observe that the NCs' surface passivation influences the diffusive trajectories of voids and the resulting degree of structural protection.…”

“…[ 5 ] The increase in photoluminescence of NCs and efficiency of bulk perovskite solar cells [ 6–10 ] are assigned to the diffusion of defects to grain boundaries, accompanied by crystal facet reconstruction at room temperature. [ 11 ] Self‐healing is the spontaneous ability of a crystal to anneal and recover from structural damage. Compared to conductors and polymers, the self‐healing of semiconductors is relatively rare.…”