Nanocrystals of Lead Chalcohalides: A Series of Kinetically Trapped Metastable Nanostructures

Toso, Stefano; Akkerman, Quinten A.; Martín‐García, Beatriz; Prato, Mirko; Zito, Juliette; Infante, Ivan; Dang, Zhiya; Moliterni, Anna; Giannini, Cinzia; Bladt, Eva; Lobato, Iván; Ramade, Julien; Bals, Sara; Buha, Joka; Spirito, Davide; Mugnaioli, Enrico; Gemmi, Mauro; Manna, Liberato

doi:10.1021/jacs.0c03577

Cited by 39 publications

(84 citation statements)

References 87 publications

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“…The models discussed above give us important hints on how to build a model of the heterostructure for our DFT calculations. For the CsPbX 3 perovskite cube we have simply taken one of our “trap-free” models of about 3.2 nm in size published earlier, 29 whereas for the lead chalcohalide we first cleaved the bulk into a sphere of 4.2 nm diameter with a charge balanced stoichiometry ( Figure 3 a), and then we relaxed the structure and computed its density of states. This shows a large number of surface defects, as evidenced by the inverse participation ratio (IPR) analysis ( Figure 4 a).…”

Section: Resultsmentioning

confidence: 99%

Halide Perovskite–Lead Chalcohalide Nanocrystal Heterostructures

et al. 2021

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We report the synthesis of colloidal CsPbX3–Pb4S3Br2 (X = Cl, Br, I) nanocrystal heterostructures, providing an example of a sharp and atomically resolved epitaxial interface between a metal halide perovskite and a non-perovskite lattice. The CsPbBr3–Pb4S3Br2 nanocrystals are prepared by a two-step direct synthesis using preformed subnanometer CsPbBr3 clusters. Density functional theory calculations indicate the creation of a quasi-type II alignment at the heterointerface as well as the formation of localized trap states, promoting ultrafast separation of photogenerated excitons and carrier trapping, as confirmed by spectroscopic experiments. Postsynthesis reaction with either Cl– or I– ions delivers the corresponding CsPbCl3–Pb4S3Br2 and CsPbI3–Pb4S3Br2 heterostructures, thus enabling anion exchange only in the perovskite domain. An increased structural rigidity is conferred to the perovskite lattice when it is interfaced with the chalcohalide lattice. This is attested by the improved stability of the metastable γ phase (or “black” phase) of CsPbI3 in the CsPbI3–Pb4S3Br2 heterostructure.

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Section: Resultsmentioning

confidence: 99%

Halide Perovskite–Lead Chalcohalide Nanocrystal Heterostructures

et al. 2021

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“… 56 On a broader perspective, knowing how nanocrystals transform can help prevent or exploit such transformations. For example, halide migration can probably be halted in compounds with mixed covalent/ionic bonding such as chalcohalides 57 or metal–halide compounds in which the formation energy of halide vacancies is high. Growing a shell even a few layers thick of such materials on halide perovskite nanocrystals might prevent them from undergoing anion exchange and other unwanted reactions.…”

Section: Discussionmentioning

confidence: 99%

Metamorphoses of Cesium Lead Halide Nanocrystals

2021

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Conspectus Following the impressive development of bulk lead-based perovskite photovoltaics, the “perovskite fever” did not spare nanochemistry. In just a few years, colloidal cesium lead halide perovskite nanocrystals have conquered researchers worldwide with their easy synthesis and color-pure photoluminescence. These nanomaterials promise cheap solution-processed lasers, scintillators, and light-emitting diodes of record brightness and efficiency. However, that promise is threatened by poor stability and unwanted reactivity issues, throwing down the gauntlet to chemists. More generally, Cs–Pb–X nanocrystals have opened an exciting chapter in the chemistry of colloidal nanocrystals, because their ionic nature and broad diversity have challenged many paradigms established by nanocrystals of long-studied metal chalcogenides, pnictides, and oxides. The chemistry of colloidal Cs–Pb–X nanocrystals is synonymous with change: these materials demonstrate an intricate pattern of shapes and compositions and readily transform under physical stimuli or the action of chemical agents. In this Account, we walk through four types of Cs–Pb–X nanocrystal metamorphoses: change of structure, color, shape, and surface. These transformations are often interconnected; for example, a change in shape may also entail a change of color. The ionic bonding, high anion mobility due to vacancies, and preservation of cationic substructure in the Cs–Pb–X compounds enable fast anion exchange reactions, allowing the precise control of the halide composition of nanocrystals of perovskites and related compounds (e.g., CsPbCl 3 ⇄ CsPbBr 3 ⇄ CsPbI 3 and Cs 4 PbCl 6 ⇄ Cs 4 PbBr 6 ⇄ Cs 4 PbI 6 ) and tuning of their absorption edge and bright photoluminescence across the visible spectrum. Ion exchanges, however, are just one aspect of a richer chemistry. Cs–Pb–X nanocrystals are able to capture or release (in short, trade) ions or even neutral species from or to the surrounding environment, causing major changes to their structure and properties. The trade of neutral PbX 2 units allows Cs–Pb–X nanocrystals to cross the boundaries among four different types of compounds: 4CsX + PbX 2 ⇄ Cs 4 PbBr 6 + 3PbX 2 ⇄ 4CsPbBr 3 + PbX 2 ⇄ 4CsPb 2 X 5 . These reactions do not occur at random, because the reactant and product nanocrystals are connected by the Cs + cation substructure preservation principle, stating that ion trade reactions can transform one compound into another by means of distorting, expanding, or contracting their shared Cs + cation substructu...

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“…3D structural data sets from single NCs can be acquired with an extremely low electron dose rate and with minimal beam exposure, thus fitting the requirements imposed by extremely beam-sensitive materials such as MHs [30]. As an example, recently, in our efforts to explore new MH materials, we synthesized Cs 3 Cu 4 In 2 Cl 13 NCs exhibiting a novel perovskiterelated structure whose resolution could be reached only via 3D-ED in combination with powder XRD (Box 1) [9,34].…”

Section: Structural Resolutionmentioning

confidence: 99%

“…In the case of a new, unknown (nano)crystal structure, its ab initio solution can be achieved through 3D electron diffraction, which can be further supported, if necessary, by high-angle annular dark-field imaging (HAADF) performed in a scanning transmission electron microscope (HAADF-STEM) and high-resolution transmission electron microscope (HTEM) analyses. Adapted, with permission, from [7,34].…”

Section: Trends Trends In In Chemistry Chemistrymentioning

confidence: 99%