Organic–inorganic hybrid perovskite quantum wells exhibit electronic structures with properties intermediate between those of inorganic semiconductors and molecular crystals. In these systems, periodic layers of organic spacer molecules occupy the interstitial spaces between perovskite sheets, thereby confining electronic excitations to two dimensions. Here, we investigate spectroscopic line broadening mechanisms for phonons coupled to excitons in lead-iodide layered perovskites with phenyl ethyl ammonium (PEA) and azobenzene ethyl ammonium (AzoEA) spacer cations. Using a modified Elliot line shape analysis for the absorbance and photoluminescence spectra, polaron binding energies of 11.2 and 17.5 meV are calculated for (PEA)2PbI4 and (AzoEA)2PbI4, respectively. To determine whether the polaron stabilization processes influence the dephasing mechanisms of coupled phonons, five-pulse coherent Raman spectroscopies are applied to the two systems under electronically resonant conditions. The prominence of inhomogeneous line broadening mechanisms detected in (AzoEA)2PbI4 suggests that thermal fluctuations involving the deformable organic phase broaden the distributions of phonon frequencies within the quantum wells. In addition, our data indicate that polaron stabilization primarily involves photoinduced reorganization of the organic phases for both systems, whereas the impulsively excited phonons represent less than 10% of the total polaron binding energy. The signal generation mechanisms associated with our fifth-order coherent Raman experiments are explored with a perturbative model in which cumulant expansions are used to account for time-coincident vibrational dephasing and polaron stabilization processes.
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21 August 2024
Research Article|
August 19 2024
Elucidating phonon dephasing mechanisms in layered perovskites with coherent Raman spectroscopies
Special Collection:
Time-resolved Vibrational Spectroscopy
Zijian Gan
;
Zijian Gan
(Investigation, Methodology, Writing – original draft)
Department of Chemistry, University of North Carolina at Chapel Hill
, Chapel Hill, North Carolina 27599, USA
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Camryn J. Gloor
;
Camryn J. Gloor
(Investigation, Methodology, Writing – original draft)
Department of Chemistry, University of North Carolina at Chapel Hill
, Chapel Hill, North Carolina 27599, USA
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Liang Yan
;
Liang Yan
(Investigation, Methodology)
Department of Chemistry, University of North Carolina at Chapel Hill
, Chapel Hill, North Carolina 27599, USA
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Xiaowei Zhong
;
Xiaowei Zhong
(Investigation, Methodology)
Department of Chemistry, University of North Carolina at Chapel Hill
, Chapel Hill, North Carolina 27599, USA
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Wei You
;
Wei You
(Funding acquisition, Supervision)
Department of Chemistry, University of North Carolina at Chapel Hill
, Chapel Hill, North Carolina 27599, USA
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Andrew M. Moran
Andrew M. Moran
a)
(Funding acquisition, Investigation, Methodology, Supervision, Writing – original draft)
Department of Chemistry, University of North Carolina at Chapel Hill
, Chapel Hill, North Carolina 27599, USA
a)Author to whom correspondence should be addressed: [email protected]
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a)Author to whom correspondence should be addressed: [email protected]
J. Chem. Phys. 161, 074202 (2024)
Article history
Received:
April 29 2024
Accepted:
July 29 2024
Citation
Zijian Gan, Camryn J. Gloor, Liang Yan, Xiaowei Zhong, Wei You, Andrew M. Moran; Elucidating phonon dephasing mechanisms in layered perovskites with coherent Raman spectroscopies. J. Chem. Phys. 21 August 2024; 161 (7): 074202. https://doi.org/10.1063/5.0216472
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