Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 61: Frontiers in Electronic-Structure Theory - Focus on Electron-Phonon Interactions III (joint session O/CPP/DS/HL)

O 61.1: Invited Talk

Wednesday, March 18, 2020, 10:30–11:00, GER 38

Hybrid Perovskites: polarons, excitons and phase diagrams — •Georg Kresse, Menno Bokdam, and Ryosuke Jinnouchi — University of Vienna, Faculty of Physics and Center for Computational Materials Sciences

Halide perovskites are very promising solar cell materials. The first part of this presentation studies the formation of polarons and excitons in MAPbI3. We show that both, polarons and excitons, possess about similar binding energies. To obtain accurate results, the calculations have to be carefully converged with respect to the k-point sampling, something that has been often "overlooked" in the past [1].

The second part of the talk presents studies on the finite temperature behavior of MAPbI3. To achieve the required long simulation time and large length scales, an on-the-fly machine learning scheme that generates force fields automatically during first principles molecular dynamics simulations is used. This force field opens up the required time and length scales, while retaining the distinctive chemical precision of first principles methods [2]. Using machine learned potentials, isothermal-isobaric simulations give direct insight into the underlying microscopic mechanisms of the phase transitions. We observe that MAPbI3 is an very dynamic material even at room temperature, putting some question marks on the hereto considered static models.

[1] M. Bokdam, T. Sander, A. Stroppa, S. Picozzi, D. D. Sarma, C. Franchini, G. Kresse, Scientific Rep. 6, 28618 (2016); [2] R. Jinnouchi, J. Lahnsteiner, F. Karsai, G. Kresse, M. Bokdam, PRL 122, 225701 (2019).