Stable Mott Polaron State Limits the Charge Density in Lead Halide Perovskites

Heng Zhang; Elke Debroye; Beatriz Vina-Bausa; Donato Valli; Shuai Fu; Wenhao Zheng; Lucia Di Virgilio; Lei Gao; Jarvist M. Frost; Aron Walsh; Johan Hofkens; Hai I. Wang; Mischa Bonn

doi:10.1021/acsenergylett.2c01949

Stable Mott Polaron State Limits the Charge Density in Lead Halide Perovskites

Heng Zhang, Elke Debroye, Beatriz Vina-Bausa, Donato Valli, Shuai Fu, Wenhao Zheng, Lucia Di Virgilio, Lei Gao, Jarvist M. Frost, Aron Walsh, Johan Hofkens, Hai I. Wang, Mischa Bonn

Department of Materials Science and Engineering

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

1 Citation (Scopus)

Abstract

Large polarons are known to form in lead halide perovskites (LHPs). Photoinduced isolated polarons at low densities have been well-researched, but many-body interactions at elevated polaron densities, exceeding the Mott criterion (i.e., Mott polaron density), have remained elusive. Here, employing ultrafast terahertz spectroscopy, we identify a stable Mott polaron state in LHPs at which the polaron wavefunctions start to overlap. The Mott polaron density is determined to be ∼10¹⁸ cm^-3, in good agreement with theoretical calculations based on the Feynman polaron model. The electronic phase transition across the Mott density is found to be universal in LHPs and independent of the constituent ions. Exceeding the Mott polaron density, excess photoinjected charge carriers annihilate quickly within tens to hundreds of picoseconds, before reaching the stable and long-lived Mott state. These results have considerable implications for LHP-based devices and for understanding exotic phenomena reported in LHPs.

Original language	English
Pages (from-to)	420-428
Number of pages	9
Journal	ACS Energy Letters
Volume	8
Issue number	1
DOIs	https://doi.org/10.1021/acsenergylett.2c01949
Publication status	Published - 2023 Jan 13

Bibliographical note

Funding Information:
We thank Jaco Geuchies, Maksim Grechko, and Heejae Kim for fruitful discussions and constructive comments. E.D. acknowledges financial support from the Research Foundation - Flanders (FWO Grant No. S002019N) and from the KU Leuven Research Fund (KUL grant No. STG/21/010). J.H. acknowledges financial support from the Research Foundation - Flanders (FWO Grant Nos. G.0B39.15, G.0B49.15, G098319N, S002019N, and ZW15_09-GOH6316), from the Flemish government through long-term structural funding Methusalem (CASAS2, Meth/15/04), from the KU Leuven Research Fund (iBOF-21-085 PERSIST), and from the MPI as a fellow. D.V. acknowledges the Research Foundation - Flanders for his Ph.D. fellowship (FWO Grant No 1S45221N). S.F. acknowledges fellowship support from the Chinese Scholarship Council (CSC). L.D.V. acknowledges support from the EU Horizon 2020 Framework Programme (Grant No. 811284).

Funding Information:
Open access funded by Max Planck Society.

Publisher Copyright:
© 2022 The Authors. Published by 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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title = "Stable Mott Polaron State Limits the Charge Density in Lead Halide Perovskites",

abstract = "Large polarons are known to form in lead halide perovskites (LHPs). Photoinduced isolated polarons at low densities have been well-researched, but many-body interactions at elevated polaron densities, exceeding the Mott criterion (i.e., Mott polaron density), have remained elusive. Here, employing ultrafast terahertz spectroscopy, we identify a stable Mott polaron state in LHPs at which the polaron wavefunctions start to overlap. The Mott polaron density is determined to be ∼1018 cm-3, in good agreement with theoretical calculations based on the Feynman polaron model. The electronic phase transition across the Mott density is found to be universal in LHPs and independent of the constituent ions. Exceeding the Mott polaron density, excess photoinjected charge carriers annihilate quickly within tens to hundreds of picoseconds, before reaching the stable and long-lived Mott state. These results have considerable implications for LHP-based devices and for understanding exotic phenomena reported in LHPs.",

author = "Heng Zhang and Elke Debroye and Beatriz Vina-Bausa and Donato Valli and Shuai Fu and Wenhao Zheng and {Di Virgilio}, Lucia and Lei Gao and Frost, {Jarvist M.} and Aron Walsh and Johan Hofkens and Wang, {Hai I.} and Mischa Bonn",

note = "Funding Information: We thank Jaco Geuchies, Maksim Grechko, and Heejae Kim for fruitful discussions and constructive comments. E.D. acknowledges financial support from the Research Foundation - Flanders (FWO Grant No. S002019N) and from the KU Leuven Research Fund (KUL grant No. STG/21/010). J.H. acknowledges financial support from the Research Foundation - Flanders (FWO Grant Nos. G.0B39.15, G.0B49.15, G098319N, S002019N, and ZW15_09-GOH6316), from the Flemish government through long-term structural funding Methusalem (CASAS2, Meth/15/04), from the KU Leuven Research Fund (iBOF-21-085 PERSIST), and from the MPI as a fellow. D.V. acknowledges the Research Foundation - Flanders for his Ph.D. fellowship (FWO Grant No 1S45221N). S.F. acknowledges fellowship support from the Chinese Scholarship Council (CSC). L.D.V. acknowledges support from the EU Horizon 2020 Framework Programme (Grant No. 811284). Funding Information: Open access funded by Max Planck Society. Publisher Copyright: {\textcopyright} 2022 The Authors. Published by American Chemical Society.",

year = "2023",

month = jan,

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doi = "10.1021/acsenergylett.2c01949",

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T1 - Stable Mott Polaron State Limits the Charge Density in Lead Halide Perovskites

AU - Zhang, Heng

AU - Debroye, Elke

AU - Vina-Bausa, Beatriz

AU - Valli, Donato

AU - Fu, Shuai

AU - Zheng, Wenhao

AU - Di Virgilio, Lucia

AU - Gao, Lei

AU - Frost, Jarvist M.

AU - Walsh, Aron

AU - Hofkens, Johan

AU - Wang, Hai I.

AU - Bonn, Mischa

N1 - Funding Information: We thank Jaco Geuchies, Maksim Grechko, and Heejae Kim for fruitful discussions and constructive comments. E.D. acknowledges financial support from the Research Foundation - Flanders (FWO Grant No. S002019N) and from the KU Leuven Research Fund (KUL grant No. STG/21/010). J.H. acknowledges financial support from the Research Foundation - Flanders (FWO Grant Nos. G.0B39.15, G.0B49.15, G098319N, S002019N, and ZW15_09-GOH6316), from the Flemish government through long-term structural funding Methusalem (CASAS2, Meth/15/04), from the KU Leuven Research Fund (iBOF-21-085 PERSIST), and from the MPI as a fellow. D.V. acknowledges the Research Foundation - Flanders for his Ph.D. fellowship (FWO Grant No 1S45221N). S.F. acknowledges fellowship support from the Chinese Scholarship Council (CSC). L.D.V. acknowledges support from the EU Horizon 2020 Framework Programme (Grant No. 811284). Funding Information: Open access funded by Max Planck Society. Publisher Copyright: © 2022 The Authors. Published by American Chemical Society.

PY - 2023/1/13

Y1 - 2023/1/13

N2 - Large polarons are known to form in lead halide perovskites (LHPs). Photoinduced isolated polarons at low densities have been well-researched, but many-body interactions at elevated polaron densities, exceeding the Mott criterion (i.e., Mott polaron density), have remained elusive. Here, employing ultrafast terahertz spectroscopy, we identify a stable Mott polaron state in LHPs at which the polaron wavefunctions start to overlap. The Mott polaron density is determined to be ∼1018 cm-3, in good agreement with theoretical calculations based on the Feynman polaron model. The electronic phase transition across the Mott density is found to be universal in LHPs and independent of the constituent ions. Exceeding the Mott polaron density, excess photoinjected charge carriers annihilate quickly within tens to hundreds of picoseconds, before reaching the stable and long-lived Mott state. These results have considerable implications for LHP-based devices and for understanding exotic phenomena reported in LHPs.

AB - Large polarons are known to form in lead halide perovskites (LHPs). Photoinduced isolated polarons at low densities have been well-researched, but many-body interactions at elevated polaron densities, exceeding the Mott criterion (i.e., Mott polaron density), have remained elusive. Here, employing ultrafast terahertz spectroscopy, we identify a stable Mott polaron state in LHPs at which the polaron wavefunctions start to overlap. The Mott polaron density is determined to be ∼1018 cm-3, in good agreement with theoretical calculations based on the Feynman polaron model. The electronic phase transition across the Mott density is found to be universal in LHPs and independent of the constituent ions. Exceeding the Mott polaron density, excess photoinjected charge carriers annihilate quickly within tens to hundreds of picoseconds, before reaching the stable and long-lived Mott state. These results have considerable implications for LHP-based devices and for understanding exotic phenomena reported in LHPs.

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DO - 10.1021/acsenergylett.2c01949

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SN - 2380-8195

VL - 8

SP - 420

EP - 428

JO - ACS Energy Letters

JF - ACS Energy Letters

IS - 1

ER -

Stable Mott Polaron State Limits the Charge Density in Lead Halide Perovskites

Abstract

Bibliographical note

All Science Journal Classification (ASJC) codes

UN SDGs

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