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Title: Large polaron self-trapped states in three-dimensional metal-halide perovskites
Authors: Wong, Walter P. D.
Yin, Jun
Chaudary, Bhumika
Chin, Xin Yu
Cortecchia, Daniele
Lo, Shu-Zee A.
Grimsdale, Andrew C.
Mohammed, Omar F.
Lanzani, Guglielmo
Soci, Cesare
Keywords: Engineering::Materials::Energy materials
Science::Physics::Optics and light
Issue Date: 2020
Source: Wong, W. P. D., Yin, J., Chaudary, B., Chin, X. Y., Cortecchia, D., Lo, S. A., Grimsdale, A. C., Mohammed, O. F., Lanzani, G. & Soci, C. (2020). Large polaron self-trapped states in three-dimensional metal-halide perovskites. ACS Materials Letters, 2(1), 20-27.
Project: NRF-CRP14-2014-03 
Journal: ACS Materials Letters
Abstract: In recent years, metal halide perovskites have generated tremendous interest for optoelectronic applications and their underlying fundamental properties. Due to the large electron-phonon coupling characteristic of soft lattices, self-trapping phenomena are expected to dominate hybrid perovskite photoexcitation dynamics. Yet, while the photogeneration of small polarons was proven in low dimensional perovskites, the nature of polaron excitations in technologically relevant 3D perovskites, and their influence on charge carrier transport, remain elusive. In this study, we used a combination of first principle calculations and advanced spectroscopy techniques spanning the entire optical frequency range to pin down polaron features in 3D metal halide perovskites. Mid-infrared photoinduced absorption shows the photogeneration of states associated to low energy intragap electronic transitions with lifetime up to the ms time scale, and vibrational mode renormalization in both frequency and amplitude. Density functional theory supports the assignment of the spectroscopic features to large polarons leading to new intra gap transitions, hardening of phonon mode frequency, and renormalization of the oscillator strength. Theory provides quantitative estimation for the charge carrier masses and mobilities increase upon polaron formation, confirming experimental results. Overall, this work contributes to complete the scenario of elementary photoexcitations in metal halide perovskites and highlights the importance of polaronic transport in perovskite-based optoelectronic devices.
ISSN: 2639-4979
DOI: 10.1021/acsmaterialslett.9b00276
Rights: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Materials Letters, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SPMS Journal Articles

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