SKM 2021 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 1: Focus Session: When theory meets experiment: Hybrid halide perovskites for applications beyond solar

HL 1.1: Invited Talk

Monday, September 27, 2021, 10:00–10:30, H4

Phonon Screening of Excitons in Halide Perovskites and Beyond — •Marina Filip — University of Oxford, Department of Physics

The interaction of photoexcited bound electron-hole pairs (excitons) is screened by both electrons and by polar phonons. For organic-inorganic lead-halide perovskites, theoretical and experimental evidence suggests that ionic vibrations have an important contribution to the dielectric screening [1,2]. However, state of the art GW/BSE methodology for studying electronic and optical excitations does not capture phonon screening effects. In this talk I will present our recently developed framework based on GW/BSE, to include phonon screening effects [3]. I will show that phonon screening contributes to significantly reduce the exciton binding energy, and demonstrate this effect for lead halide perovskites, CsPbX3 (X = Cl, Br, I), as well as other well known semiconductors and insulators. Furthermore, I will show our generalization of the Wannier-Mott model to include phonon screening effects, and discuss general trends for the phonon screening contribution to the exciton binding energy.

[1] Miyata et al, Nat. Phys. 11, 582 (2015) [2] Umari et al, JPCL, 9 , 3 ,620 (2018) [3] Filip, Haber & Neaton, PRL, in press (2021)

This work was supported by the US Department of Energy and the UK EPSRC. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC) and the Texas Advanced Computing Center (TACC) through the NSF-funded XSEDE program.