Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 2: Organic-inorganic perovskite semiconductors (with O)
HL 2.6: Vortrag
Montag, 16. März 2015, 10:45–11:00, ER 164
Band structure and optical absorption of halide organometal perovskites from first principles — •Menno Bokdam, Tobias Sander, Cesare Franchini, and Georg Kresse — University of Vienna, Faculty of Physics, Sensengasse 8, A-1090 Vienna, Austria
The high efficiency of lead halide organic perovskite solar cells has raised many questions on the mechanisms at work here. An accurate description of the macroscopic dielectric properties is essential for understanding the origin of the materials ability to convert light to electricity. In this talk, we present an accurate account of the electronic, optical and excitonic properties of twelve halide organometal perovskites ABX3 (A = CH3NH3+, HC(NH2)2+; B = Pb,Sn; X = Cl,Br,I) by means of many-body first principles methods. We use optimized structures obtained at room temperature using parallel tempering molecular dynamics. Quasi particle band structures and absorption spectra are calculated at the GW0 level. Electron-hole interactions have been included in the dielectric function by solving a Bethe-Salpeter equation for the polarizability. We demonstrate that a description beyond independent particles is necessary to describe the onset of the optical absorption. The calculated degree of localization of the excitons in k-space indicates Wannier-Mott type excitons with binding energies ranging from 30 meV (ABI3) and 100-200 meV (ABCl3). To validate our predictions, we compare the results with available experimental data (band gap and optical absorption).