The nature of dynamic local order in CH3NH3PbI3 and CH3NH3PbBr3

Weadock, Nicholas J.; Sterling, Tyler C.; Vigil, Julian A.; Gold‐Parker, Aryeh; Smith, Ian C. P.; Ahammed, Ballal; Krogstad, Matthew; Ye, Feng; Voneshen, David; Gehring, Peter; Rappe, Andrew M.; Steinrück, Hans‐Georg; Ertekin, Elif; Karunadasa, Hemamala I.; Reznik, D.; Toney, Michael F.

doi:10.1016/j.joule.2023.03.017

Cited by 27 publications

(17 citation statements)

References 58 publications

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“…Combining these two observations, the local tilt domain in the cubic phase has a shape analogous to a plate, which is roughly 1 unit cell thick and has a radius of 3 unit cells long. This analysis is consistent with the plate-like domains suggested from neutron scattering of CsPbBr 3 by Lanigan-Atkins et al which have also been found in CH 3 NH 3 PbI 3 . , …”

Section: Resultssupporting

confidence: 91%

Structural Dynamics Descriptors for Metal Halide Perovskites

Liang,

Klarbring,

Baldwin

et al. 2023

J. Phys. Chem. C

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Metal halide perovskites have shown extraordinary performance in solar energy conversion technologies. They have been classified as "soft semiconductors" due to their flexible cornersharing octahedral networks and polymorphous nature. Understanding the local and average structures continues to be challenging for both modeling and experiments. Here, we report the quantitative analysis of structural dynamics in time and space from molecular dynamics simulations of perovskite crystals. The compact descriptors provided cover a wide variety of structural properties, including octahedral tilting and distortion, local lattice parameters, molecular orientations, as well as their spatial correlation. To validate our methods, we have trained a machine learning force field (MLFF) for methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) using an on-the-fly training approach with Gaussian process regression. The known stable phases are reproduced, and we find an additional symmetry-breaking effect in the cubic and tetragonal phases close to the phase-transition temperature. To test the implementation for large trajectories, we also apply it to 69,120 atom simulations for CsPbI 3 based on an MLFF developed using the atomic cluster expansion formalism. The structural dynamics descriptors and Python toolkit are general to perovskites and readily transferable to more complex compositions.

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Section: Resultssupporting

confidence: 91%

Structural Dynamics Descriptors for Metal Halide Perovskites

Liang,

Klarbring,

Baldwin

et al. 2023

J. Phys. Chem. C

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“…Halide perovskites, however, exhibit extreme anharmonicity, , in particular for the zone boundary modes that are connected to the octahedral tilting . We also note that similar observations of short-range correlations in halide perovskites have been made experimentally for CsPbBr 3 by Lanigan-Atkins et al and for CH 3 NH 3 PbI 3 and CH 3 NH 3 PbBr 3 by Weadock et al, as well as computationally for CsPbI 3 by Baldwin et al…”

Section: Resultsmentioning

confidence: 99%

Quantifying Dynamic Tilting in Halide Perovskites: Chemical Trends and Local Correlations

Wiktor,

Fransson,

Kubicki

et al. 2023

Chem. Mater.

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Halide perovskites have emerged as one of the most interesting materials for optoelectronic applications due to their favorable properties, such as defect tolerance and long charge carrier lifetimes, which are attributed to their dynamic softness. However, this softness has led to apparent disagreements between the local instantaneous and global average structures of these materials. In this study, we rationalize this situation through an assessment of the local tilt angles of octahedra in the perovskite structure using large-scale molecular dynamics simulations based on machine-learned potentials trained using density functional theory calculations. We compare structural properties given by different density functionals [local density approximation, PBE, PBE + D3, PBEsol, strongly constrained and appropriately normed (SCAN), SCAN + rVV10, and van der Waals density functional with consistent exchange] and establish trends across a family of CsMX3 perovskites with M = Sn or Pb and X = Cl, Br or I. Notably, we demonstrate strong short-range ordering in the cubic phase of halide perovskites. This ordering is reminiscent of the tetragonal phase and provides the bridge between the disordered local structure and the global cubic arrangement. Our results provide a deeper understanding of the structural properties of halide perovskites and their local distortions, which is crucial for further understanding their optoelectronic properties.

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“…Unique nanocrystal stability is in-part contributed to a modified MHP phase space introduced at the nanoscale, where high surface-to-volume ratios allow surface energy a significant role in moderating the degree of octahedral tilting via size-dependent tensile strain. , It should be noted that accurate structure determination of MHP systems often requires care and high-resolution diffraction data, the lack of which has historically driven debate over reported structures in the literature. Subtle diffraction peak splitting for the lower symmetry perovskite phases in combination with Scherrer peak-broadening effects of nanocrystals and twinning contribute to difficult phase identification. − This goes even without mentioning dynamic local order distinct from the observed average crystal structure, necessitating inelastic and total scattering techniques. , Further study of static and dynamic local order in MHP nanocrystals is necessary to accurately describe sources of homogeneous line width broadening in the soft ionic lattices that are otherwise ill described from an assignment of the average crystal structure. , …”

Section: Current State Of Knowledge and Technology By Materialsmentioning

confidence: 99%

“…555−557 This goes even without mentioning dynamic local order distinct from the observed average crystal structure, necessitating inelastic and total scattering techniques. 558,559 Further study of static and dynamic local order in MHP nanocrystals is necessary to accurately describe sources of homogeneous line width broadening in the soft ionic lattices that are otherwise ill described from an assignment of the average crystal structure. The inorganic CsPbX 3 MHP nanocrystals are the most frequently studied systems, generally due to their narrow, excitonic, and nanosecond radiative decay but also due to their relative stability compared to hybrid systems with more volatile components.…”

Section: B-site Metal Cation and Plqymentioning

confidence: 99%

Design Rules for Obtaining Narrow Luminescence from Semiconductors Made in Solution

et al. 2023

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Solution-processed semiconductors are in demand for present and next-generation optoelectronic technologies ranging from displays to quantum light sources because of their scalability and ease of integration into devices with diverse form factors. One of the central requirements for semiconductors used in these applications is a narrow photoluminescence (PL) line width. Narrow emission line widths are needed to ensure both color and single-photon purity, raising the question of what design rules are needed to obtain narrow emission from semiconductors made in solution. In this review, we first examine the requirements for colloidal emitters for a variety of applications including light-emitting diodes, photodetectors, lasers, and quantum information science. Next, we will delve into the sources of spectral broadening, including “homogeneous” broadening from dynamical broadening mechanisms in single-particle spectra, heterogeneous broadening from static structural differences in ensemble spectra, and spectral diffusion. Then, we compare the current state of the art in terms of emission line width for a variety of colloidal materials including II–VI quantum dots (QDs) and nanoplatelets, III–V QDs, alloyed QDs, metal–halide perovskites including nanocrystals and 2D structures, doped nanocrystals, and, finally, as a point of comparison, organic molecules. We end with some conclusions and connections, including an outline of promising paths forward.

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The nature of dynamic local order in CH3NH3PbI3 and CH3NH3PbBr3

Cited by 27 publications

References 58 publications

Structural Dynamics Descriptors for Metal Halide Perovskites

Structural Dynamics Descriptors for Metal Halide Perovskites

Quantifying Dynamic Tilting in Halide Perovskites: Chemical Trends and Local Correlations

Design Rules for Obtaining Narrow Luminescence from Semiconductors Made in Solution

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