Electron Phonon Coupling in Lead Halide Perovskites: Impact of Dynamic Disorder and Phonon-Phonon Scattering
Nuri Yazdani a
a Institute of Electronics (IfE), D-ITET, ETHZ
Proceedings of International Conference on Emerging Light Emitting Materials (EMLEM23)
Peyia, Cyprus, 2023 November 13th - 15th
Organizers: Grigorios Itskos, Maksym Kovalenko and Maryna Bodnarchuk
Invited Speaker, Nuri Yazdani, presentation 020
Publication date: 18th August 2023

The coupling of phonons to the elementary excitations of a material determines its excited state properties and the rates of dynamical processes. The strength of Electron-Phonon Coupling (EPC) therefore dictates the performance metrics of applications utilizing a material. Stronger EPC increases the rate of non-radiative recombination of charge carriers, ultimately limiting the efficiency of semiconductor devices. For applications utilizing luminescence, stronger EPC leads to broadening of the emission spectrum reducing its spectral purity, and drives decoherence and loss of information in single coherent photon sources. Strong electron-phonon coupling, however, is not always detrimental, as exemplified by the case of superconductivity. To understand the intrinsic limitations or aptitude of a material for a given application, precise determination of its phonons and how they couple to transitions is required. Additionally, through material engineering, one can aim to tune EPC in a material system in order to improve performance metrics. To achieve this, detailed understanding of the mechanistic origins of EPC in the material is required.

In this talk I will review recent studies we have performed to quantify EPC in lead-halide perovskites. Ab-initio calculations indicate strong deformation potential type coupling to low energy optical phonons, vibrational modes which drive octahedral tilting in lead-halide perovskites. Optical-pump diffraction-probe, single dot luminescence, and time resolved emission measurements on lead-halide perovskite nanocrystals corroborate this finding, and confirm that deformation potential coupling to octahedral tilting is the dominant coupling to the excitation/recombination of excitons in LHPs. The dependence of strength of this EPC on temperature and on the LHP composition (and phase) point to strong enhancement of the EPC as a result of dynamic structural disorder and phonon-phonon scattering.

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