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

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

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 languageEnglish
Pages (from-to)420-428
Number of pages9
JournalACS Energy Letters
Volume8
Issue number1
DOIs
StatePublished - 13 Jan 2023

Bibliographical note

Publisher Copyright:
© 2022 The Authors. Published by American Chemical Society.

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