The Nature of Dynamic Local Order in CH3NH3Pbl3 and CH3NH3PbBr3

Published

May 17, 2023

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

Pub Type

Journals

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DOI Link

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 CH₃NH₃Pbl₃ and CH₃NH₃PbBr₃, Joule, [online], https://dx.doi.org/10.1016/j.joule.2023.03.017 (Accessed April 27, 2024)