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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 10: Focus Session: When theory meets experiment: Hybrid halide perovskites for applications beyond solar I (joint session HL/CPP)
CPP 10.2: Hauptvortrag
Montag, 16. März 2020, 10:00–10:30, POT 251
Lattice Screening of Excitons in Lead Halide Perovskites from First Principles — •Marina R. Filip1, Jonah B. Haber2, and Jeffrey B. Neaton2,3,4 — 1Department of Physics, University of Oxford — 2Department of Physics, UC Berkeley — 3Molecular Foundry and Materials Science Division, Lawrence Berkeley National Laboratory — 4Kavli Energy NanoSciences Institute at Berkeley
Dielectric screening in semiconducting and insulating crystals generally originates both from electrons and polar phonons. Since photoexcited electron-hole pairs interact within this dielectric environment, both the electronic and lattice components of the screening can have important contributions to excitonic properties; for lead-halide perovskites, this is suggested from both theoretical and experimental evidence [1,2]. However, standard ab initio GW-BSE methodology for calculating optical excitations does not capture dynamic lattice polarization effects. In this talk I will present our extension of the GW-BSE method, to include lattice contributions to the screening. I will show that in heteropolar semiconductors with weakly bound excitons, dynamic lattice polarization can significantly reduce the exciton binding energy, and I will demonstrate this effect for the CsPbX3 (X = Cl, Br, I) perovskites. Furthermore, I will discuss more generally the lattice contribution to the exciton binding energy in heteropolar semiconductors, as it emerges from a generalization of the Wannier-Mott model to include dynamical lattice polarization effects. [1] Miyata et al, Nat. Phys. 11, 582 (2015) [2] Umari et al, JPCL, 9, 3, 620 (2018). Work supported by the US DoE in the C2SEPEM center; computational resources from NERSC.