Calculating polaron mobility in halide perovskites

Jarvist Moore Frost
Phys. Rev. B 96, 195202 – Published 7 November 2017

Abstract

Lead halide perovskite semiconductors are soft, polar materials. The strong driving force for polaron formation (the dielectric electron-phonon coupling) is balanced by the light band effective masses, leading to a strongly-interacting large polaron. A first-principles prediction of mobility would help understand the fundamental mobility limits. Theories of mobility need to consider the polaron (rather than free-carrier) state due to the strong interactions. In this material we expect that at room temperature polar-optical phonon mode scattering will dominate and so limit mobility. We calculate the temperature-dependent polaron mobility of hybrid halide perovskites by variationally solving the Feynman polaron model with the finite-temperature free energies of Ōsaka. This model considers a simplified effective-mass band structure interacting with a continuum dielectric of characteristic response frequency. We parametrize the model fully from electronic-structure calculations. In methylammonium lead iodide at 300K we predict electron and hole mobilities of 133 and 94cm2V1s1, respectively. These are in acceptable agreement with single-crystal measurements, suggesting that the intrinsic limit of the polaron charge carrier state has been reached. Repercussions for hot-electron photoexcited states are discussed. As well as mobility, the model also exposes the dynamic structure of the polaron. This can be used to interpret impedance measurements of the charge-carrier state. We provide the phonon-drag mass renormalization and scattering time constants. These could be used as parameters for larger-scale device models and band-structure dependent mobility simulations.

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  • Received 12 May 2017
  • Revised 19 October 2017

DOI:https://doi.org/10.1103/PhysRevB.96.195202

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Jarvist Moore Frost*

  • Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom and Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom

  • *jarvist.frost@imperial.ac.uk

See Also

Charge transport in hybrid halide perovskites

Mingliang Zhang, Xu Zhang, Ling-Yi Huang, Hai-Qing Lin, and Gang Lu
Phys. Rev. B 96, 195203 (2017)

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Vol. 96, Iss. 19 — 15 November 2017

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