Elucidating the Weakly Reversible Cs–Pb–Br Perovskite Nanocrystal Reaction Network with High-Throughput Maps and Transformations

Abstract

Advances in automation and data analytics can aid exploration of the complex chemistry of nanoparticles. Lead halide perovskite colloidal nanocrystals provide an interesting proving ground: there are reports of many different phases and transformations, which has made it hard to form a coherent conceptual framework for their controlled formation through traditional methods. In this work, we systematically explore the portion of Cs-Pb-Br synthesis space in which many optically distinguishable species are formed using high-throughput robotic synthesis to understand their formation reactions. We deploy an automated method that allows us to determine the relative amount of absorbance that can be attributed to each species in order to create maps of the synthetic space. These in turn facilitate improved understanding of the interplay between kinetic and thermodynamic factors that underlie which combination of species are likely to be prevalent under a given set of conditions. Based on these maps, we test potential transformation routes between perovskite nanocrystals of different shapes and phases. We find that shape is determined kinetically, but many reactions between different phases show equilibrium behavior. We demonstrate a dynamic equilibrium between complexes, monolayers and nanocrystals of lead bromide, with substantial impact on the reaction outcomes. This allows us to construct a chemical reaction network that qualitatively explains our results as well as previous reports and can serve as a guide for those seeking to prepare a particular composition and shape. File list (2) download file view on ChemRxiv perovskite synthesis SI revision submission.pdf (12.37 MiB) download file view on ChemRxiv perovskite synthesis paper revision submission.pdf (2.42 MiB) S 1 Supporting Information for: Elucidating the weakly reversible Cs-Pb-Br perovskite nanocrystal reaction network with high-throughput maps and transformations

Structure and Surface Passivation of Ultrathin Cesium Lead Halide Nanoplatelets Revealed by Multilayer Diffraction

“…In this work, we prepared Cs–Pb–Br nanoplatelets with a lateral dimension of a few dozens of nanometers ( Figure 1 a) via a previously published procedure. 40 The films of oriented nanoplatelets for the Multilayer Diffraction analysis were prepared by slowly drying a suspension of nanoplatelets in hexane on top of a tilted silicon wafer. Upon the successful film deposition, a region of the substrate became covered by a smooth and iridescent film and was selected for the diffraction experiment.…”

“…For quantum-confined platelets, the thickness can be estimated through the absorption spectrum: in our case, it matched with reports for ∼12 Å thick nanoplatelets (excitonic absorption peak at 428 nm, Figure 2 a). 12 , 40 , 43 Taking the CsPbBr 3 crystal structure as a reference, where the Pb–Br bonds are about ∼3 Å long, the nanoplatelets must be composed of five alternating CsBr and PbBr 2 layers. To complete the nanoplatelet model, we had to provide a description for the surface as well.…”

Bandgap determination from individual orthorhombic thin cesium lead bromide nanosheets by electron energy-loss spectroscopy

“…17 Platelets as thin as monolayers have been recently identified from optical data analysis, as a product of high-throughput robotic synthesis inside a mixture of other species. 18 In summary, different possible phases were reported for nanostructures of CsPbBr 3 with reduced dimensions. In this communication we address the structure of CsPbBr 3 in the form of thin nanosheets (NS, with thickness t down to 4 nm).…”

High‐Throughput Robotic Synthesis and Photoluminescence Characterization of Aqueous Multinary Copper–Silver Indium Chalcogenide Quantum Dots

“…In this regard, the best strategies for a high-throughput NC production are associated with robotized synthetic procedures and auto matized characterization protocols allowing human-related uncertainty factors to be excluded. Such methods are currently in a rapid development for other promising materials, such as luminescent binary II-VI QDs [8][9][10][11] and hybrid perovskite microand nanocrystals, [12][13][14][15][16][17][18][19][20] but are still to be realized for multinary metal-chalcogenide NC light absorbers and emitters.…”