Regensburg 2016 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 12: Photovoltaics (Joint session of HL and DF, organized by HL)
HL 12.7: Vortrag
Montag, 7. März 2016, 17:00–17:15, H2
Role of Polar Phonons in the Photo Excited State of Metal Halide Perovskites — Menno Bokdam1, Tobias Sander1, Alessandro Stroppa2, Silvia Picozzi2, •D.D. Sarma3, Cesare Franchini1, and Georg Kresse1 — 1Faculty of Physics, Computational Materials Physics, University of Vienna, Austria — 2Consiglio Nazionale delle Ricerche - CNR-SPIN, L’Aquila, Italy — 3Indian Institute of Science, Bangalore, India
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 MAPbX3 perovskites we report on relativistic GW-BSE calculations. 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 MAPbI3, phonon modes present in this frequency range have a negligible contribution to the ionic screening. By calculating the polarisation 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.