Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 31: Organic Semiconductors IV: Excitations and Charges (jointly with HL, DS)

CPP 31.3: Vortrag

Mittwoch, 16. März 2011, 14:45–15:00, ZEU 222

Determination of the effective radiative quantum efficiency of light-emitting guest-host systems — •Tobias Schmidt¹, Daniel-Steffen Setz², Benjamin Lebsanft¹, Thomas Wehlus¹, Jörg Frischeisen¹, Benjamin Krummacher², Michael Flämmich³, Norbert Danz³, and Wolfgang Brütting¹ — ¹Experimentalphysik IV, Universität Augsburg — ²OSRAM Opto Semiconductors, Regensburg — ³Fraunhofer-Institut für angewandte Optik und Feinmechanik (IOF), Jena

The efficiency of organic light-emitting diodes (OLEDs) is still limited as only a small part of the applied electrical power is converted into light and finally extracted from the device to air. Especially the radiative quantum efficiency (RQE) of the used guest-host system is often declared to be unity in phosphorescent emitter/matrix combinations. Due to interference effects, the radiative lifetime of the emitter and thus the effective RQE of the light-emitting guest-host system is influenced by coupling to different modes of the cavity formed by the metallic mirror and the partially reflecting ITO/glass interface. The effective RQE can be determined by measuring the external quantum efficiency of the electrically driven OLED or the photoluminescence lifetime of the emitter inside the OLED at different emitter positions in the cavity. We have investigated the RQE of the commonly used emitter Ir(ppy)₃ in neat films with PMMA and CBP as matrices, yielding values of about 70 %, and compare it to OLEDs, where significantly lower values of only 40 % are obtained.