Regensburg 2013 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 32: Poster: Organic Semiconductors

CPP 32.15: Poster

Wednesday, March 13, 2013, 16:30–18:30, Poster C

Determination of molecular transition dipole orientation of organic emitters by angular-dependent photoluminescence measurements — •Christian Mayr, Tobias Schmidt, Bert Scholz, Lars Jäger, and Wolfgang Brütting — Institute of Physics, University of Augsburg, 86135 Augsburg, Germany

Organic light-emitting diodes (OLEDs) have been investigated for more than 20 years and are standing now at the frontier to mass production. Current research focuses on the enhancement of light outcoupling efficiency which is reduced especially due to the energy dissipation to surface plasmons (SPs). Numerical simulations show that a horizontal emitter orientation with respect to the substrate can enhance the efficiency by up to 50% due to reduced coupling to SPs. An expeditious method to determine the orientation of the transition dipole moment of molecules has been developed using angular dependent photoluminescence spectroscopy. By comparing measurement with simulations, the orientation can be quantitatively determined. Although other methods to measure molecular orientation exist, the presented method not only makes it possible to study molecular orientation in neat thin films but also of small amounts of emitters doped into a matrix material without knowing any detailed information of the optical properties of the dopant. Hence, this method is particularly useful for the investigation of newly developed materials. The method is applied to Iridium-based phosphorescent emitters in order to gain a consistent efficiency analysis of OLEDs and possibilities to enhance light outcoupling.