Berlin 2018 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 18: Perovskite and Hybrid Photovolatics
HL 18.7: Vortrag
Dienstag, 13. März 2018, 11:00–11:15, EW 203
First-principles-based modeling of atomic processes in hybrid perovskites — •Jingrui Li1, Jari Järvi1,2, Mariana Rossi3, and Patrick Rinke1 — 1Department of Applied Physics, Aalto University, Finland — 2Department of Physics, University of Helsinki, Finland — 3Fritz Haber Institute of the Max Planck Society, Theory Department, Berlin, Germany
To further advance hybrid-perovskite-based photovoltaic technology, we need to understand these materials on the atomic scale, on which the light-to-energy conversion and transport processes occur. Currently, this atomic scale is riddled with controversies. For the detachment of methylammonium (MA) cations from the PbI3 cage in MAPbI3, very low (∼10 meV) as well as high (∼100 meV) activation energies Ea have been reported. Quasi-elastic neutron scattering measurements (QENS) for the orthorhombic phase found Ea=48 meV, which was attributed to the axial rotation of the whole MA cation [1]. To shed light on this controversy, we performed density-functional theory calculations (PBE0 functional + van der Waals corrections + inclusion of nuclear quantum effects) for several rotational MA processes. For the rotation of CH3 against the NH3 unit which remains bound to the PBI3 cage, we obtain Ea=42 meV in good agreement with the QENS result. We therefore ascribe this barrier to this torsional motion. For the full axial rotation, which breaks three hydrogen bonds, we obtain a barrier of ∼130 meV which is much higher than the QENS results.
[1] Chen et al., Phys. Chem. Chem. Phys. 17 31278 (2015).