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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.8: Poster

Dienstag, 26. Februar 2008, 14:30–20:00, Poster A

Photoluminescence degradation of blue OLED emitters — •Stephan Winter, Sebastian Reineke, Karsten Walzer, and Karl Leo — Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden

Organic light-emitting diodes (OLEDs) based on small molecule materials are currently developed for applications in flat panel displays and general lighting sources. Key parameters of such devices are high efficiency, long lifetime, and appropriate colour properties. Most of the efficient deep blue emitters still suffer from rather fast degradation and, thus, require further improvement.

The aim of the present work is to gain a fundamental understanding of the intrinsic degradation processes causing the low stability of blue OLED emitters. For this purpose, we study the photoluminescence (PL) degradation instead of the most often investigated electroluminescence degradation to separate electrically and optically caused effects.

We show a newly developed PL lifetime measurement system which allows the study of degradation processes under the influence of either electron or hole currents. First, we demonstrate the importance of a proper encapsulation for PL lifetime. Next, using this set-up, we demonstrate the very high PL stability of the highly efficient blue singlet emitter 2,2',7,7'-tetrakis(2,2-diphenylvinyl)spiro-9,9'-bifluorene (Spiro-DPVBi) under electron and hole currents and make a comparison to the lifetime of OLEDs using the same emitter.