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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 45: Perovskite and photovoltaics I (joint session HL/CPP)
CPP 45.5: Vortrag
Dienstag, 17. März 2020, 10:30–10:45, POT 251
Structural Influence on the Exciton Fine Structure of Cesium Lead Halide Quantum Dots — •Torben Steenbock and Gabriel Bester — Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, 20146 Hamburg, Germany.
Cesium lead halide quantum dots (QDs) show a bright emission, which makes them interesting for applications in optoelectronics. The origin of the bright emission is still under debate. One suggestion [1] is based on a theoretical effective mass model assuming a very strong Rashba effect, which would leads to an unusual bright exciton ground state. Another explanation is based on the idea of a phonon bottleneneck, wich leads to an efficient emission from the higher-energy bright state [2] without dark ground state.
We calculate the exciton fine structure splitting (FSS) based on ab-initio density functional theory combined with a screened configuration interaction approach for small CsPbX3 (X=Cl,Br,I) QDs. We find that the bright-dark splitting for Cl, Br, and I CsPbX3 perovskites amount to 17, 12 and 5 meV, respectively, with only small changes due to the symmetry (cubic, tetragonal, orthorhombic) so that we always obtain a dark ground state. The FSS (splitting between the bright states) is sensitive to the symmetry with splittings of up to 5 meV for the lowest symmetry orthorhombic structures.
[1] P.C. Sercel et al., Nano Lett. 2019, 19, 4068–4077.
[2] P. Tamarat et al., Nat. Mater. 2019, 18, 717–724.