Hamburg 2001 – scientific programme
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SYOF: Organische Festkörper
SYOF 5: Poster Session
SYOF 5.39: Poster
Tuesday, March 27, 2001, 17:00–19:00, Aula S3
High efficiency organic light emitting diodes based on triplet harvesting materials — •Arvid Hunze1, Marcus Scheffel1, Jan Birnstock1, Jörg Blässing1, Matthias Stößel1, Karsten Heuser1, Georg Wittmann1, Wolfgang Rogler1, and Albrecht Winnacker2 — 1Siemens AG, ZT Mf 1, Paul-Gossen-Str. 100, 91052 Erlangen — 2Universität Erlangen-Nürnberg, Institut für Werkstoffwissenschaften, Martensstr. 7, 91058 Erlangen
One new and promising way to improve the quantum efficiency of organic
light emitting diodes (OLEDs) is the usage of electrophosphorescent
materials. Due to the long lifetime of triplet excitation of an emitting
molecule, phosphorescent decay is suppressed. Thus conventional materials
such as Alq3, show emission primarily from singulet excited states. As
the ratio between fluorescent singulet and phosphorescent triplet states in
small molecule OLEDs is 1:3, the harvesting of triplets is expected to has
the potential to increase the luminous efficiency by a factor of four.
Transition metal complexes like Ir[ppy]3 and PtOEP show a fast and
efficient phosphorescent decay, leading to very high external quantum
efficiencies. We present investigations on electrophosphorescent molecules
doped into various charge transport materials. By using combinatorial
methods, the dopant concentration is varied over a wide range, and the
effects of different concentrations are investigated. 20 cd/A and 15 lm/W
at 100 cd/m2 have been reached with devices with Ir[ppy]3 doped
in CBP.