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HL: Fachverband Halbleiterphysik

HL 66: Focus Session (CPP with HL): Hybrid photovoltaics and perovskites I

HL 66.8: Talk

Thursday, March 19, 2015, 12:00–12:15, C 130

Quantum-Chemical Calculations of Hybrid Perovskites — •Wichard J. D. Beenken, Ksenia Korschunova, Mezhoura Oussadou, Lars Winterfeld, and Erich Runge — Institut für Physik und Institut für Mikro- und Nanotechnologie, Technische Universität Ilmenau, Germany

Hybrid perovskites possess a multitude of structural phases depending on temperature and the organic cations. Thus a deeper understanding of the various crystal structures and their influence on the electronic bandstructure is necessary to control the quality of these materials for solar cells. Though there exist already several structure analyses of perovskites by X-ray diffraction, the severe problem remains that the contrast of organic light atoms (C, N, H) and inorganic heavy atoms (Pb, I) is several magnitudes. This makes it difficult to determine the exact positions of the organic cations within the perovskite lattice spanned by a network of octahedral Lead-Iodid anions. Consequently, most of the published structures for hybrid perovskites do only provide guesses for the organic part, in particular for the H-atoms. Their positions, however, may be important for understanding the electronic band structure, which is also difficult to be determined experimentally, e.g. by angle resolved UPS, for the polycrystallinity of the samples. Therefore, we have done DFT calculations using the quantum-chemical package VASP 5.3for crystal structure optimization and band structure determination of low-temperature and metastable phases of several organic-inorganic hybrid perovskites.