Berlin 2018 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 36: Organic Thin Films, Organic-Inorganic Interfaces: Session II (joint session DS/CPP)

DS 36.2: Vortrag

Freitag, 16. März 2018, 09:45–10:00, H 0111

Probing the orientation of phosphorescent Iridium complexes by impedance spectroscopy — •Markus Schmid, Thomas Lampe, Alexander Hofmann, and Wolfgang Brütting — Institute of Physics, University of Augsburg, 86135 Augsburg, Germany

Impedance spectroscopy (IS) is a powerful, non-destructive method to analyze organic semiconductors and their interfaces. In organic bilayer devices, that contain one polar material, IS can be used to measure the interfacial charge density between the two semiconductors. This polarization results from partially aligned permanent dipole moments. If the permanent molecular dipole moment is known, conclusions about the molecular orientation are possible [1].

In this study we present results from IS for different polar Iridium complexes that are commonly used as emitters in organic light emitting diodes. By calculating their permanent dipole moment and their transition dipole moment via density functional theory we relate the average orientation of both vectors in the film. Additionally, the measured alignment of the molecules is compared to molecular dynamic simulations. We find good agreement between both, the often studied orientation of the transition dipole moment and the simulations.

[1] Jäger, Lars, et. al. AIP Advances 6, 095220 (2016)