SKM 2023 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 35: Focus Session: Transient multi-wave mixing on excitonic resonances

HL 35.8: Talk

Thursday, March 30, 2023, 13:00–13:15, POT 251

Time-resolved four-wave mixing spectroscopy of excitons in a FA_0.9Cs_0.1PbI_2.8Br_0.2 perovskite crystal — •Stefan Grisard¹, Artur V. Trifonov¹, Dmitry N. Dirin^2,3, Maksym V. Kovalenko^2,3, Ilya A. Akimov¹, Dmitri R. Yakovlev¹, and Manfred Bayer¹ — ¹Experimentelle Physik 2, Technische Universität Dortmund — ²Institute of Inorganic Chemistry, Department of Chemistry and Applied Bioscience, ETH Zürich — ³Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology

Formamidinium lead triiodide (FAPbI₃) shows outstanding characteristics for future photovoltaic or light emitting devices, suffers however from poor phase stability. Additives such as cesium and bromine help to improve the phase stability, but possibly increase the localization of the charge carriers. In this work, we present time resolved four-wave mixing spectroscopy as a versatile tool to investigate the coherent optical properties of a FA_0.9Cs_0.1PbI_2.8Br_0.2 crystal. At low temperatures of 1.5K, the coherent optical response is represented by photon echoes due to the strong inhomogeneous broadening of exciton resonances. We find that the coherence time T₂ is surprisingly long (≈100ps), comparable with the lifetime T₁. The spectral dependence of T₂ and T₁ indicate the importance of carrier localization.