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

Bokdam, Menno and Sander, Tobias and Stroppa, Alessandro and Picozzi, Silvia and Sarma, DD and Franchini, Cesare and Kresse, Georg (2016) Role of Polar Phonons in the Photo Excited State of Metal Halide Perovskites. In: SCIENTIFIC REPORTS, 6 .

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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) PbI3 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 `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.

Item Type:	Journal Article
Publication:	SCIENTIFIC REPORTS
Publisher:	NATURE PUBLISHING GROUP
Additional Information:	Copy right for this article belongs to the NATURE PUBLISHING GROUP, MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	25 Aug 2016 10:12
Last Modified:	25 Aug 2016 10:12
URI:	http://eprints.iisc.ac.in/id/eprint/54324

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