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  Direct Observation of Ultrafast Exciton Dissociation in Lead Iodide Perovskite by 2D Electronic Spectroscopy

Jha, A., Duan, H.-G., Tiwari, V., Nayak, P. K., Snaith, H. J., Thorwart, M., et al. (2018). Direct Observation of Ultrafast Exciton Dissociation in Lead Iodide Perovskite by 2D Electronic Spectroscopy. ACS Photonics, 5(3), 852-860. doi:10.1021/acsphotonics.7b01025.

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Additional details on sample characterization (SEM data), calculation of exciton and carrier densities, TG-FROG measurement data, global-fitting approach, and two-dimensional correlation analysis and 2D electronic spectra measured at 180 K along with the retreived 2D vibrational maps
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 Creators:
Jha, Ajay1, Author           
Duan, Hong-Guang1, 2, 3, Author           
Tiwari, Vandana1, 4, Author           
Nayak, Pabitra K.5, Author
Snaith, Henry J.5, Author
Thorwart, Michael2, 3, Author
Miller, R. J. Dwayne1, 3, 6, 7, Author           
Affiliations:
1Miller Group, Atomically Resolved Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society, ou_1938288              
2I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany, ou_persistent22              
3The Hamburg Center for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany, ou_persistent22              
4Department of Chemistry, University of Hamburg, Martin-Luther-King Platz 6, 20146 Hamburg, Germany, ou_persistent22              
5 Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom, ou_persistent22              
6Atomically Resolved Structural Dynamics Division, Max Planck Research Department for Structural Dynamics, Department of Physics, University of Hamburg, External Organizations, ou_2173636              
7he Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, Canada M5S 3H6, ou_persistent22              

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Free keywords: binding energy; electronic dephasing; exciton−phonon coupling; photovoltaics; vibrational modes; Wannier exciton
 Abstract: The unprecedented success of hybrid organic–inorganic lead halide perovskites in photovoltaics motivates fundamental research to unravel the underlying microscopic mechanism for photoinduced charge generation. Recent studies suggest that most photoexcitations in perovskites are free charge carriers, although the contribution of the electron–hole pairs (i.e., excitons) at room temperature has been a matter of debate. We have employed ultrafast two-dimensional (2D) electronic spectroscopy to directly probe the elementary optical excitation of CH3NH3PbI3 thin films with ∼16 fs temporal resolution. We distinctly capture the ultrafast dissociation of excitons to the charge carriers at room temperature and at 180 K. Interestingly, we also observe that the coherent oscillations of the off-diagonal signals in the 2D electronic spectra live for ∼50 fs at room temperature. The entropy-driven dissociation of excitons to charge carriers happens within the electronic dephasing time scale and is favored by the low exciton binding energy, which we determine to be ∼12 meV at room temperature. This ultrafast dissociation of excitons to charge carriers can be one of the important contributions to the high efficiency of perovskite-based photovoltaics.

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Language(s): eng - English
 Dates: 2017-09-082017-12-222018-03
 Publication Status: Issued
 Pages: 9
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Degree: -

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Title: ACS Photonics
Source Genre: Journal
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Publ. Info: Washington, DC : American Chemical Society
Pages: - Volume / Issue: 5 (3) Sequence Number: - Start / End Page: 852 - 860 Identifier: Other: 2330-4022
CoNE: https://pure.mpg.de/cone/journals/resource/2330-4022