Exciton-polaron dynamics in lead halide perovskite nanocrystals

Helene Seiler^a^,^b, Daniela Zahn^a, Victoria C.A. Taylor^a, Maryna I. Bodnarchuk^c, Yoav W. Windsor^a^,^d, Maksym Kovalenko^e^,^c, Ralph Ernstorfer^a^,^d

^aFritz Haber Institute of the Max Planck Society, Department of Physical Chemistry, 14195 Berlin, Germany

^bFreie Universität Berlin, Arnimallee 14, Berlin, Germany

^cLaboratory for Thin Films and Photovoltaics, Empa – Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland

^dTechnische Universität Berlin, Straße des 17. Juni 124, Berlin, Germany

^eETHZ

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Spring 2024 Conference (MATSUS24)

#PeroQuant24 - Halide perovskites for quantum technologies

Barcelona, Spain, 2024 March 4th - 8th

Organizers: Simon Boehme, Sascha Feldmann and Maksym Kovalenko

Invited Speaker, Helene Seiler, presentation 090
DOI: https://doi.org/10.29363/nanoge.matsus.2024.090
Publication date: 18th December 2023

Lead halide perovskites have attracted tremendous attention, initially for their performance in thin film photovoltaics, and more recently for a variety of remarkable optical properties. Defect tolerance through polaron formation within the ionic lattice is a key aspect of these materials. In recent studies [1,2], some of us have applied two-dimensional electronic spectroscopy (2DES) to probe the timescale and amplitude of the electronic gap correlations in lead halide perovskite nanocrystals via homogeneous lineshape dynamics. The 2DES data reveal irreversible, diffusive dynamics that are consistent with liquid-like structural dynamics on the 100 femtosecond timescale. These dynamics were assigned to the optical signature of polaron formation, the conceptual solid-state analogue of solvation.

To complement the 2DES data, we have employed the method of femtosecond electron diffraction (FED) to directly measure the sub-picosecond lattice dynamics of weakly confined CsPbBr3 nanocrystals following above-gap photoexcitation. The data reveal a light-induced structural distortion appearing on a time scale varying between 380 and 1200 fs depending on the excitation fluence. We attribute these dynamics to the effect of exciton–polarons on the lattice and the slower dynamics at high fluences to slower sub-picosecond hot-carrier cooling, which slows down the establishment of the exciton–polaron population. Further analysis and simulations show that the distortion is consistent with motions of the [PbBr3]− octahedral ionic cage, and closest agreement with the data is obtained for Pb–Br bond lengthening.

Together, the 2DES and FED data offer a unique and complementary view of exciton-polaron dynamics in lead halide perovskite nanocrystals.

References:

[1] Seiler, H., Palato, S., Sonnichsen, C. et al. Two-dimensional electronic spectroscopy reveals liquid-like lineshape dynamics in CsPbI3 perovskite nanocrystals. Nat Commun 10, 4962 (2019).

[2] Patrick Brosseau, Arnab Ghosh, Helene Seiler, Dallas Strandell, Patanjali Kambhampati; Exciton–polaron interactions in metal halide perovskite nanocrystals revealed via two-dimensional electronic spectroscopy. J. Chem. Phys. 14 November 2023; 159 (18): 184711.

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