Ultrafast Charge Carrier Relaxation in Inorganic Halide Perovskite Single Crystals Probed by Two-Dimensional Electronic Spectroscopy

Xuan Trung Nguyen; Daniel Timmer; Yevgeny Rakita; David Cahen; Alexander Steinhoff; Frank Jahnke; Christoph Lienau; Antonietta De Sio

doi:10.1021/acs.jpclett.9b01936

Ultrafast Charge Carrier Relaxation in Inorganic Halide Perovskite Single Crystals Probed by Two-Dimensional Electronic Spectroscopy

Xuan Trung Nguyen, Daniel Timmer, Yevgeny Rakita, David Cahen, Alexander Steinhoff, Frank Jahnke, Christoph Lienau, Antonietta De Sio

Research output: Contribution to journal › Article › peer-review

18 Scopus citations

Abstract

Halide perovskites are promising optoelectronic materials. Despite impressive device performance, especially in photovoltaics, the femtosecond dynamics of elementary optical excitations and their interactions are still debated. Here we combine ultrafast two-dimensional electronic spectroscopy (2DES) and semiconductor Bloch equations (SBEs) to probe the room-temperature dynamics of nonequilibrium excitations in CsPbBr₃ crystals. Experimentally, we distinguish between excitonic and free-carrier transitions, extracting a ∼30 meV exciton binding energy, in agreement with our SBE calculations and with recent experimental studies. The 2DES dynamics indicate remarkably short, <30 fs carrier relaxation at a ∼3 meV/fs rate, much faster than previously anticipated for this material, but similar to that in direct band gap semiconductors such as GaAs. Dynamic screening of excitons by free carriers also develops on a similarly fast <30 fs time scale, emphasizing the role of carrier-carrier interactions for this material's optical properties. Our results suggest that strong electron-phonon couplings lead to ultrafast relaxation of charge carriers, which, in turn may limit halide perovskites' carrier mobilities.

Original language	English
Pages (from-to)	5414-5421
Number of pages	8
Journal	Journal of Physical Chemistry Letters
Volume	10
Issue number	18
DOIs	https://doi.org/10.1021/acs.jpclett.9b01936
State	Published - 19 Sep 2019
Externally published	Yes

Bibliographical note

Publisher Copyright:
© 2019 American Chemical Society.

Funding

Financial support by the Deutsche Forschungsgemeinschaft (SPP1839 and SPP1840), the Korea Foundation for International Cooperation of Science and Technology (Global Research Laboratory project, K20815000003) and the German-Israeli Foundation (Grant No. 1256) is gratefully acknowledged. The Oldenburg group thanks Ephraim Sommer and Katrin Winte for assistance during the early stages of this project. A.D.S. also thanks Martin Silies for kindly sharing the computer facility used for the 2DES simulations. A.S. and F.J. thank Matthias Florian for fruitful discussions.

Funders	Funder number
Korea Foundation for International Cooperation of Science and Technology	K20815000003
Deutsche Forschungsgemeinschaft	SPP1840, SPP1839
German-Israeli Foundation for Scientific Research and Development	1256

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abstract = "Halide perovskites are promising optoelectronic materials. Despite impressive device performance, especially in photovoltaics, the femtosecond dynamics of elementary optical excitations and their interactions are still debated. Here we combine ultrafast two-dimensional electronic spectroscopy (2DES) and semiconductor Bloch equations (SBEs) to probe the room-temperature dynamics of nonequilibrium excitations in CsPbBr3 crystals. Experimentally, we distinguish between excitonic and free-carrier transitions, extracting a ∼30 meV exciton binding energy, in agreement with our SBE calculations and with recent experimental studies. The 2DES dynamics indicate remarkably short, <30 fs carrier relaxation at a ∼3 meV/fs rate, much faster than previously anticipated for this material, but similar to that in direct band gap semiconductors such as GaAs. Dynamic screening of excitons by free carriers also develops on a similarly fast <30 fs time scale, emphasizing the role of carrier-carrier interactions for this material's optical properties. Our results suggest that strong electron-phonon couplings lead to ultrafast relaxation of charge carriers, which, in turn may limit halide perovskites' carrier mobilities.",

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Ultrafast Charge Carrier Relaxation in Inorganic Halide Perovskite Single Crystals Probed by Two-Dimensional Electronic Spectroscopy

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