Role of Polar Phonons in the Photo Excited State of Metal Halide Perovskites

Author(s)
Menno Bokdam, Tobias Sander, Alessandro Stroppa, Silvia Picozzi, D. D. Sarma, Cesare Franchini, Georg Kresse
Abstract

The development of high efficiency perovskite solar cells has sparked a multitude of measurements on the optical properties of these materials. For the most studied methylammonium(MA)PbI 3 perovskite, a large range (6-55 meV) of exciton binding energies has been reported by various experiments. The existence of excitons at room temperature is unclear. For the MAPbX 3 perovskites we report on relativistic Bethe-Salpeter Equation calculations (GW-BSE). This method is capable to directly calculate excitonic properties from first-principles. At low temperatures it predicts exciton binding energies in agreement with the reported â € large' values. For MAPbI 3, phonon modes present in this frequency range have a negligible contribution to the ionic screening. By calculating the polarization in time from finite temperature molecular dynamics, we show that at room temperature this does not change. We therefore exclude ionic screening as an explanation for the experimentally observed reduction of the exciton binding energy at room temperature and argue in favor of the formation of polarons.

Organisation(s)
Computational Materials Physics
External organisation(s)
Institute of Genetics and Biophysics "Adriano Buzzati-Traverso", CNR, Indian Institute of Science
Journal
Scientific Reports
Volume
6
No. of pages
8
ISSN
2045-2322
DOI
https://doi.org/10.1038/srep28618
Publication date
06-2016
Peer reviewed
Yes
Austrian Fields of Science 2012
103009 Solid state physics, 103015 Condensed matter, 103025 Quantum mechanics, 103036 Theoretical physics
Keywords
Portal url
https://ucris.univie.ac.at/portal/en/publications/role-of-polar-phonons-in-the-photo-excited-state-of-metal-halide-perovskites(26d02102-6218-4e77-b34b-4ab5015d7824).html