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Title: Acoustic phonon lifetimes limit thermal transport in methylammonium lead iodide

Hybrid organic-inorganic perovskites (HOIPs) have become an important class of semiconductors for solar cells and other optoelectronic applications. Electron-phonon coupling plays a critical role in all optoelectronic devices, and although the lattice dynamics and phonon frequencies of HOIPs have been well studied, little attention has been given to phonon lifetimes. We report high-precision momentum - resolved measurements of acoustic phonon lifetimes in the hybrid perovskite methylammonium lead iodide ( MAPI ), using inelastic neutron spectroscopy to provide high energy resolution and fully deuterated single crystals to reduce incoherent scattering from hydrogen. Our measurements reveal extremely short lifetimes on the order of picoseconds, corresponding to nanometer mean free paths and demonstrating that acoustic phonons are unable to dissipate heat efficiently. Lattice-dynamics calculations using ab-initio third-order perturbation theory indicate that the short lifetimes stem from strong three-phonon interactions and a high density of low-energy optical phonon modes related to the degrees of freedom of the organic cation. Such short lifetimes have significant implications for electron-phonon coupling in MAPI and other HOIPs, with direct impacts on optoelectronic devices both in the cooling of hot carriers and in the transport and recombination of band edge carriers. These findings illustrate a fundamental difference between HOIPsmore » and conventional photovoltaic semiconductors and demonstrate the importance of understanding lattice dynamics in the effort to develop metal halide perovskite optoelectronic devices.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [3] ;  [6] ;  [5] ;  [7]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  4. Univ. of Bath, Bath (United Kingdom)
  5. Stanford Univ., Stanford, CA (United States)
  6. Kings College London, London (United Kingdom)
  7. Imperial College London, London (United Kingdom); Yonsei Univ., Seoul (Korea)
Publication Date:
Grant/Contract Number:
AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 115; Journal Issue: 47; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; hybrid perovskite; thermal conductivity; inelastic neutron spectroscopy; lattice dynamics; solar cells
OSTI Identifier:
1480457
Alternate Identifier(s):
OSTI ID: 1481042

Toney, Michael, Gold-Parker, Aryeh, Gehring, Peter M., Skelton, Jonathan M., Smith, Ian C., Parshall, Dan, Frost, Jarvist M., Karunadasa, Hemamala I., and Walsh, Aron. Acoustic phonon lifetimes limit thermal transport in methylammonium lead iodide. United States: N. p., Web. doi:10.1073/pnas.1812227115.
Toney, Michael, Gold-Parker, Aryeh, Gehring, Peter M., Skelton, Jonathan M., Smith, Ian C., Parshall, Dan, Frost, Jarvist M., Karunadasa, Hemamala I., & Walsh, Aron. Acoustic phonon lifetimes limit thermal transport in methylammonium lead iodide. United States. doi:10.1073/pnas.1812227115.
Toney, Michael, Gold-Parker, Aryeh, Gehring, Peter M., Skelton, Jonathan M., Smith, Ian C., Parshall, Dan, Frost, Jarvist M., Karunadasa, Hemamala I., and Walsh, Aron. 2018. "Acoustic phonon lifetimes limit thermal transport in methylammonium lead iodide". United States. doi:10.1073/pnas.1812227115.
@article{osti_1480457,
title = {Acoustic phonon lifetimes limit thermal transport in methylammonium lead iodide},
author = {Toney, Michael and Gold-Parker, Aryeh and Gehring, Peter M. and Skelton, Jonathan M. and Smith, Ian C. and Parshall, Dan and Frost, Jarvist M. and Karunadasa, Hemamala I. and Walsh, Aron},
abstractNote = {Hybrid organic-inorganic perovskites (HOIPs) have become an important class of semiconductors for solar cells and other optoelectronic applications. Electron-phonon coupling plays a critical role in all optoelectronic devices, and although the lattice dynamics and phonon frequencies of HOIPs have been well studied, little attention has been given to phonon lifetimes. We report high-precision momentum - resolved measurements of acoustic phonon lifetimes in the hybrid perovskite methylammonium lead iodide ( MAPI ), using inelastic neutron spectroscopy to provide high energy resolution and fully deuterated single crystals to reduce incoherent scattering from hydrogen. Our measurements reveal extremely short lifetimes on the order of picoseconds, corresponding to nanometer mean free paths and demonstrating that acoustic phonons are unable to dissipate heat efficiently. Lattice-dynamics calculations using ab-initio third-order perturbation theory indicate that the short lifetimes stem from strong three-phonon interactions and a high density of low-energy optical phonon modes related to the degrees of freedom of the organic cation. Such short lifetimes have significant implications for electron-phonon coupling in MAPI and other HOIPs, with direct impacts on optoelectronic devices both in the cooling of hot carriers and in the transport and recombination of band edge carriers. These findings illustrate a fundamental difference between HOIPs and conventional photovoltaic semiconductors and demonstrate the importance of understanding lattice dynamics in the effort to develop metal halide perovskite optoelectronic devices.},
doi = {10.1073/pnas.1812227115},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 47,
volume = 115,
place = {United States},
year = {2018},
month = {11}
}

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Ab initiomolecular dynamics for liquid metals
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