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The Nature of Dynamic Local Order in CH3NH3Pbl3 and CH3NH3PbBr3

Published

Author(s)

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

Abstract

Hybrid lead halide perovskites (LHPs) are a class of semiconductor with novel physical properties and impressive optoelectronic performance that are distinctively governed by structural fluctuations. [1, 2] Diffraction experiments sensitive to average, long range order reveal a cubic structure in the device-relevant, high-temperature phase. [3, 4] Local probes, however, find a lower symmetry structure. [5–7] Resolving this discrepancy and uncovering the nature of the lower symmetry structure is key to determining the unusual structure-function relation- ships in hybrid LHPs, including the long carrier lifetimes and facile halide migration. We use single-crystal X-ray and neutron diffuse scattering and neutron inelastic spectroscopy combined with molecular dynamics calculations to investigate the true structure of two prototypical hybrid perovskites CH3NH3PbI3and CH3NH3PbBr3. We observe and visualize remarkable collective dynamics within the cubic phase where a network of fluctuating, local two-dimensional pancake- like regions of tilted lead halide octahedra (lower symmetry) induce longer range intermolecular correlations within the CHd3^NH+3 sublattice. This dynamic local structure can introduce transient ferroelectric or antiferroelectric domains that increase charge carrier lifetimes [8], and the lifetime of the 2D tilted regions is long enough to affect strongly the halide migration, a poorly understood degradation mechanism [9].
Citation
Joule
Volume
7
Issue
5

Keywords

photovoltaics, lead-halide perovskites, perovskites, diffuse scattering, neutron scattering, x-ray scattering, molecular dynamics simulations

Citation

Weadock, N. , Sterling, T. , Vigil, J. , Gold-Parker, A. , Smith, I. , Ahammed, B. , Krogstad, M. , Ye, F. , Voneshen, D. , Gehring, P. , Rappe, A. , Steinruck, H. , Ertekin, E. , Karunadasa, H. , Reznik, D. and Toney, M. (2023), The Nature of Dynamic Local Order in CH<sub>3</sub>NH<sub>3</sub>Pbl<sub>3</sub> and CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub>, Joule, [online], https://dx.doi.org/10.1016/j.joule.2023.03.017 (Accessed June 22, 2024)

Issues

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Created May 17, 2023, Updated January 23, 2024