Nucleation, Growth, and Structural Transformations of Perovskite Nanocrystals

Abstract

Despite the recent surge of interest in lead halide perovskite nanocrystals, there are still significant gaps in the understanding of nucleation and growth processes involved in their formation. Using CsPbX 3 as a model system, we systematically study the formation mechanism of cubic CsPbX 3 nanocrystals, their growth via oriented attachment into larger nanostructures, and the associated phase transformations. We found evidence to support that the formation of CsPbX 3 NCs occurs through the seed-mediated nucleation method, where Pb°NPs formed during the course of reaction act as seeds. Further growth occurs through self-assembly and oriented attachment. The polar environment is a major factor in determining the structure and shape of the resulting nanoparticles, as confirmed by experiments with aged seed reaction mixtures, and by addition of polar additives. These results provide a fundamental understanding of the influence of the environment polarity on self-assembly, self-healing, and the ability to control the morphology and structure over the perovskite structures. As a result of this understanding, we were able to extend the synthesis to produce other materials such as CsPbBr 3 nanowires and orthorhombic CsPbI 3 nanowires with tunable length ranging from 200 nm to several microns.

Atomic Characterization of Byproduct Nanoparticles on Cesium Lead Halide Nanocrystals Using High-Resolution Scanning Transmission Electron Microscopy

“…Figure 2b In addition, metallic Pb NPs were also found on CsPbBr 3 NCs using high-resolution STEM-HAADF. [26], the Pb NPs found here at a high magnification (electron dose 1.9 × 10 5 e − /Å 2 ) may, to a large extent, originate from the as-reported electron radiation effect on CsPbBr 3 lattice [23][24][25]. From Figure 3b, it is clear to see that the CsPbBr 3 lattices under the as-observed Pb NP were modified and damaged.…”

“…Recent studies have consistently reported the observation of nanoparticles (NPs) with high contrast to LHP nanocrystals (CH 3 NH 3 PbBr 3 [21] and CsPbBr 3 [22][23][24][25][26]) in transmission electron microscopy (TEM) images (i.e., the white dots in Figure 1). However, the structure, chemistry, and forming mechanism of these NPs are still unclear and under debate in these reports.…”

“…However, the structure, chemistry, and forming mechanism of these NPs are still unclear and under debate in these reports. Some reports indicate that these NPs are Pb metal, originating from either the precursor material PbBr 2 [26], or the electron damaged CsPbBr 3 lattices [23][24][25]. One report suggests that these NPs are PbBr 2 [21] and another report claims that these NPs are CsPb 2 Br 5 [22].…”

Fully‐Inorganic Trihalide Perovskite Nanocrystals: A New Research Frontier of Optoelectronic Materials

“…[84] As known to all, size uniformity is the most critical factor in exploiting the size-dependent properties of NCs. In this procedure, the non-coordination solvent used is 1-octadecene, while OA and OAm are chosen as the ligands for stabilizing the resulting NCs.…”

“…[77] Copyright 2016, American Chemical Society. [76,84] [75] However, the dominated parameter accounting for a decrease of the width of nanowires was not elucidated.…”