Dresden 2014 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 19: Poster Session 1 (joint session with BP)
CPP 19.30: Poster
Tuesday, April 1, 2014, 09:30–13:00, P1
Characterization of quenching processes on the external quantum efficiency of phosphorescent organic light-emitting diodes — •Sebastian Wehrmeister1, Tobias D. Schmidt1, Wolfgang Brütting1, Daniel S. Setz2, Thomas Wehlus2, Andreas F. Rausch2, and Thilo C. G. Reusch2 — 1Institute of Physics, University of Augsburg, Germany — 2OSRAM Opto Semiconductors GmbH, Regensburg, Germany
Efficiency roll-off in organic light-emitting diodes (OLEDs) as result of high current densities represents a substantial drawback for technical applications. However, since high brightness is a major request for lighting purposes, high current densities are unavoidable. To identify and analyse the impact of quenching processes on the efficiency, time-resolved spectral measurements on a red phosphorescent OLED with Iridium(III)bis(2-methyldibenzo-[f,h]quinoxaline)(acetylacetonate) (Ir(MDQ)2(acac)) as emitter have been performed. We probe the excited states lifetime after a short laser pulse on top of the steady-state region of a rectangular electrical pulse [1]. By continuously increasing the current density of the electrical pulse, the non-radiative decay becomes more likely and the excited states lifetime decreases. A comparison of the calculated external quantum efficiency (EQE) based on these data with direct EQE measurements reveals the influence and the origin of quenching processes on the efficiency roll-off of the device.
[1] N. C. Giebink, S. R. Forrest, Phys. Rev. B, 235215-1 (2008)