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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 22: Perovskite and Photovoltaics II (joint session HL/KFM)

KFM 22.9: Talk

Thursday, March 21, 2024, 11:45–12:00, EW 203

Photon echo spectroscopy of CsPbI₃ nanocrystals — Artur V. Trifonov^1,2, •Mario Alex Hollberg¹, Stefan Grisard¹, Elena V. Kolobkova^3,4, Maria S. Kuznetsov², Mikhail O. Nestoklon¹, Jan Kaspari⁵, Doris Reiter⁵, Dmitri R. Yakovlev^1,6, Manfred Bayer¹, and Ilya A. Akimov¹ — ¹Experimentelle Physik 2, Technische Universität Dortmund — ²St. Petersburg, Russia — ³St. Petersburg, Russia — ⁴St. Petersburg, Russia — ⁵Condensed Matter Theory, Technische Universität Dortmund — ⁶St. Petersburg, Russia

All-inorganic halide perovskite nanocrystals hold potential for future optoelectronic technologies. One of the paths to fully unlock their capabilities, is a deeper understanding of coherent exciton dynamics in these materials. In this work, we investigated a caesium lead tri-iodide (CsPbI₃) nanocrystal ensemble using time-resolved photon echo spectroscopy at cryogenic temperatures (1.5 K). We observed a long exciton lifetime T₁ of about 1 ns and an exciton coherence time T₂ of up to approximately 300 ps. The initial tens of picoseconds in the photon echo decay exhibited oscillatory behavior with two most pronounced frequencies of 3.2 meV and 5.1 meV, which we attribute to the interaction between excitons and optical phonons. The exciton fine structure manifests itself at lower oscillation frequencies of 0.2 meV and 1.1 meV.

Keywords: Exciton; Photon Echo; Perovskite nanocrystal ensemble; Coherent optical phonons; Exciton fine structure