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Understanding Electron–Phonon Interactions in 3D Lead Halide Perovskites from the Stereochemical Expression of 6s² Lone Pairs

Huang, Xu and Li, Xiaotong and Tao, Yu and Guo, Songhao and Gu, Jiazhen and Hong, Huilong and Yao, Yige and Guan, Yan and Gao, Yunan and Li, Chen and Lü, Xujie and Fu, Yongping (2022) Understanding Electron–Phonon Interactions in 3D Lead Halide Perovskites from the Stereochemical Expression of 6s² Lone Pairs. Journal of the American Chemical Society, 144 (27). pp. 12247-12260. ISSN 0002-7863. doi:10.1021/jacs.2c03443.

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The electron–phonon (e–ph) interaction in lead halide perovskites (LHPs) plays a role in a variety of physical phenomena. Unveiling how the local lattice distortion responds to charge carriers is a critical step toward understanding the e–ph interaction in LHPs. Herein, we advance a fundamental understanding of the e–ph interaction in LHPs from the perspective of stereochemical activity of 6s² lone-pair electrons on the Pb²⁺ cation. We demonstrate a model system based on three LHPs with distinctive lone-pair activities for studying the structure–property relationships. By tuning the A-cation chemistry, we synthesized single-crystal CsPbBr₃, (MA_(0.13)EA_(0.87))PbBr₃ (MA⁺ = methylammonium; EA⁺ = ethylammonium), and (MHy)PbBr₃ (MHy⁺ = methylhydrazinium), which exhibit stereo-inactive, dynamic stereo-active, and static stereo-active lone pairs, respectively. This gives rise to distinctive local lattice distortions and low-frequency vibrational modes. We find that the e–ph interaction leads to a blue shift of the band gap as temperature increases in the structure with the dynamic stereo-active lone pair but to a red shift in the structure with the static stereo-active lone pair. Furthermore, analyses of the temperature-dependent low-energy photoluminescence tails reveal that the strength of the e–ph interaction increases with increasing lone-pair activity, leading to a transition from a large polaron to a small polaron, which has significant influence on the emission spectra and charge carrier dynamics. Our results highlight the role of the lone-pair activity in controlling the band gap, phonon, and polaronic effect in LHPs and provide guidelines for optimizing the optoelectronic properties, especially for tin-based and germanium-based halide perovskites, where stereo-active lone pairs are more prominent than their lead counterparts.

Item Type:Article
Related URLs:
URLURL TypeDescription
Li, Xiaotong0000-0001-7107-7273
Guo, Songhao0000-0003-0570-0164
Hong, Huilong0000-0003-4776-9063
Gao, Yunan0000-0002-3131-7559
Li, Chen0000-0003-2115-8694
Lü, Xujie0000-0001-8402-7160
Fu, Yongping0000-0003-3362-2474
Additional Information:© 2022 American Chemical Society. Received 31 March 2022. Published online 29 June 2022. Published in issue 13 July 2022. Y.F. thanks Peking University and Beijing National Laboratory for Molecular Sciences for startup funding. The measurements of H NMR, SCXRD, and time-resolved optical spectroscopy were performed at the Analytical Instrumentation Center of Peking University/the Center for Physicochemical Analysis and Measurements in ICCAS. Dr. Jie Su’s help in single-crystal XRD measurements is acknowledged. Dr. Tianping Ying’s help in the synthesis of CsEuBr₃ is acknowledged. The authors declare no competing financial interest. Accession Codes. CCDC 2163293–2163302 contain the supplementary crystallographic data for this paper.
Funding AgencyGrant Number
Peking UniversityUNSPECIFIED
Beijing National Laboratory for Molecular SciencesUNSPECIFIED
Subject Keywords:Chemical structure, Electrical conductivity, Field emission, Lattices, Perovskites
Issue or Number:27
Record Number:CaltechAUTHORS:20220715-744499000
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Official Citation:Understanding Electron–Phonon Interactions in 3D Lead Halide Perovskites from the Stereochemical Expression of 6s² Lone Pairs Xu Huang, Xiaotong Li, Yu Tao, Songhao Guo, Jiazhen Gu, Huilong Hong, Yige Yao, Yan Guan, Yunan Gao, Chen Li, Xujie Lü, and Yongping Fu Journal of the American Chemical Society 2022 144 (27), 12247-12260 DOI: 10.1021/jacs.2c03443
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115657
Deposited By: George Porter
Deposited On:18 Jul 2022 17:39
Last Modified:18 Jul 2022 17:39

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