Slow Cooling of Hot Polarons in Halide Perovskite Solar Cells

Jarvist Moore Frost; Lucy D. Whalley; Aron Walsh

doi:10.1021/acsenergylett.7b00862

Slow Cooling of Hot Polarons in Halide Perovskite Solar Cells

Jarvist Moore Frost, Lucy D. Whalley, Aron Walsh

Department of Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

111 Citations (Scopus)

Abstract

Halide perovskites show unusual thermalization kinetics for above-bandgap photoexcitation. We explain this as a consequence of excess energy being deposited into discrete large polaron states. The crossover between low-fluence and high-fluence "phonon bottleneck" cooling is due to a Mott transition where the polarons overlap (n ≥ 10¹⁸ cm^-3) and the phonon subpopulations are shared. We calculate the initial rate of cooling (thermalization) from the scattering time in the Fröhlich polaron model to be 78 meV ps^-1 for CH₃NH₃PbI₃. This rapid initial thermalization involves heat transfer into optical phonon modes coupled by a polar dielectric interaction. Further cooling to equilibrium over hundreds of picoseconds is limited by the ultralow thermal conductivity of the perovskite lattice.

Original language	English
Pages (from-to)	2647-2652
Number of pages	6
Journal	ACS Energy Letters
Volume	2
Issue number	12
DOIs	https://doi.org/10.1021/acsenergylett.7b00862
Publication status	Published - 2017 Dec 8

Bibliographical note

Funding Information:
We thank Jonathan M. Skelton for discussions concerning the thermal conductivity calculations. Via our membership of the UK’s HEC Materials Chemistry Consortium, which is funded by EPSRC (EP/L000202), this work used the ARCHER UK National Supercomputing Service (http://www.archer.ac.uk). This work was funded by the EPSRC (Grant Numbers EP/ L01551X/1, EP/L000202, and EP/K016288/1), the Royal Society, and the ERC (Grant No. 277757).

Publisher Copyright:
© 2017 American Chemical Society.

All Science Journal Classification (ASJC) codes

Chemistry (miscellaneous)
Renewable Energy, Sustainability and the Environment
Fuel Technology
Energy Engineering and Power Technology
Materials Chemistry

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10.1021/acsenergylett.7b00862

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abstract = "Halide perovskites show unusual thermalization kinetics for above-bandgap photoexcitation. We explain this as a consequence of excess energy being deposited into discrete large polaron states. The crossover between low-fluence and high-fluence {"}phonon bottleneck{"} cooling is due to a Mott transition where the polarons overlap (n ≥ 1018 cm-3) and the phonon subpopulations are shared. We calculate the initial rate of cooling (thermalization) from the scattering time in the Fr{\"o}hlich polaron model to be 78 meV ps-1 for CH3NH3PbI3. This rapid initial thermalization involves heat transfer into optical phonon modes coupled by a polar dielectric interaction. Further cooling to equilibrium over hundreds of picoseconds is limited by the ultralow thermal conductivity of the perovskite lattice.",

author = "Frost, {Jarvist Moore} and Whalley, {Lucy D.} and Aron Walsh",

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AU - Frost, Jarvist Moore

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AU - Walsh, Aron

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PY - 2017/12/8

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AB - Halide perovskites show unusual thermalization kinetics for above-bandgap photoexcitation. We explain this as a consequence of excess energy being deposited into discrete large polaron states. The crossover between low-fluence and high-fluence "phonon bottleneck" cooling is due to a Mott transition where the polarons overlap (n ≥ 1018 cm-3) and the phonon subpopulations are shared. We calculate the initial rate of cooling (thermalization) from the scattering time in the Fröhlich polaron model to be 78 meV ps-1 for CH3NH3PbI3. This rapid initial thermalization involves heat transfer into optical phonon modes coupled by a polar dielectric interaction. Further cooling to equilibrium over hundreds of picoseconds is limited by the ultralow thermal conductivity of the perovskite lattice.

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Slow Cooling of Hot Polarons in Halide Perovskite Solar Cells

Abstract

Bibliographical note

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