Shining Light on the Structure of Lead Halide Perovskite Nanocrystals

Abstract

Lead halide perovskite nanocrystals (NCs) have attracted great attention owing to the simplicity of their synthesis and excellent defect-tolerance nature. They not only demonstrate outstanding optical and electronic properties, but also hold substantially ionic lattices with some counterintuitive structural features that are significantly different from conventional colloidal semiconductor NCs such as CdSe and InP. In this Review, we summarize and assess the recent advances in the understanding of structural characteristics of lead halide perovskite NCs. We specifically focus on the role of intrinsic defects, NC size, dopants, alloying, and external stimuli in affecting their structure. Moreover, we highlight the use of atomic resolution imaging technique in investigating their microstructural characteristics. Finally, we discuss open questions and present our perspectives on future research directions in the exciting field of science.

Synthesizing Bright CsPbBr3 Perovskite Nanocrystals with High Purification Yields and Their Composites with In Situ-Polymerized Styrene for Light-Emitting Diode Applications

“…The increase in PLQY may be related to the surface rearrangement, which removes some surface defects. 52 The corresponding average PL lifetime increases from 60.8 ns on the 1st day to 65.4 ns on the 5th day (Figure 4g and Table S1), suggesting the decrease of the defects. 53,54 The quantitative XPS analysis of the Cs, Pb, Br, and N elements shows their molar ratio of 8.8/9.7/36.0/45.5 (Figure S8).…”

Advances and Challenges in Tin Halide Perovskite Nanocrystals

“…The calculated Goldschmidt tolerance factors of CsPbI 3 and CsSnI 3 are both about 0.85, which is not within the optimal range of 0.9–1 . Previous works have uncovered that the crystal structure of Pb-based perovskites is of great relevance with the intrinsic defects, NC size, dopants, alloying, and external stimuli, which is a variety of measurement techniques . By contrast, so far there are few reports about the structures of THP NCs.…”

“…75 Previous works have uncovered that the crystal structure of Pb-based perovskites is of great relevance with the intrinsic defects, NC size, dopants, alloying, and external stimuli, which is a variety of measurement techniques. 76 By contrast, so far there are few reports about the structures of THP NCs. In this respect, our knowledge is only limited to the reported cubic phase for CsSnCl 3 NCs and the orthorhombic phase for CsSnBr 3 and CsSnI 3 NCs at room temperature, but their exact phase transition temperature still remains unclear.…”

“…In addition to surface states, our understanding of the long-range structure and defect states in the inner part of NCs remains almost blank. We envision that future works in this regard can refer to excellent demonstrations in Pb-based NCs. ,, The benefits in this direction will not only enrich the knowledge bank of defects and structure in halide perovskite NCs but also aid in intentionally tuning them to endow with near-perfect optoelectronic properties.…”

Halide Perovskite Cluster Precursors: A Paradigm for Obtaining Structure- and Color-Tunable Light-Emitting Nanocrystals

“…Semiconductor nanocrystals, which are widely known as quantum dots, have been extensively studied for more than three decades for their fabulous size-dependent color-tunable optical properties. − Among them, covalent chalcogenide nanocrystals have remained at the forefront, and fundamental insights associated with their synthesis optimizations, photophysical properties, and processing for commercialization have been widely explored. − However, in 2015, halide perovskite nanocrystals, which are dominantly ionic in nature and follow much easier synthetic pathways, emerged as a new series of nanocrystal emitters, and within a short period, they have become the workhorse in quantum dots research. − Near-unity photoluminescence quantum yields (PLQYs) remained the most important feature of these materials, and extensive research has been carried out to stabilize their bright and tunable emissions. − The fundamentals of the chemistry of their formation and insights into the phase stability of these nanocrystals have also been largely studied and are well understood. ,,,,− However, the key advancements in designing core/shell nanocrystals, facet directive growths, formation of heterostructures with covalent and plasmonic nanostructures, facet directive anisotropic growths (which remained important to induce long-term phase and optical stability), and faster carrier transportation in device or catalytic applications, still remain largely unexplored. − These require tuning of chemical parameters and also identifying selective precursors which could induce secondary growth of covalent nanostructures on specific facets of these halide perovskite nanocrystals. Moreover, optimization of the precursor ratios of A, B, and X site ions also remained critically important for stabilizing the crystal phase of ABX 3 nanocrystals or inducing other phases, such as AB 2 X 5 or A 4 BX 6 . −…”