Berlin 2005 – scientific programme

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SYOO: Organic Optoelectronics and Photonics

SYOO 6: Poster

SYOO 6.3: Poster

Monday, March 7, 2005, 18:00–20:00, Poster TU A

Highly efficient and long-living red p-i-n bottom emission OLEDs based on triplet emitter systems — •Rico Meerheim, Karsten Walzer, Martin Pfeiffer, and Karl Leo — Institut für Angewandte Photophysik (IAPP), Technische Universität Dresden, George-Bähr Str. 1, D-01062 Dresden, Germany

We demonstrate the making of highly efficient red bottom emission OLEDs with doped transport layers and phosphorescent emitter materials for high quantum yield. In this contribution we will show how the lifetime of such devices can be increased. The p-i-n devices consist of doped transport layers, charge and exciton blockers, and a dilute emitter substance inside an appropriate emitter matrix. There exists an optimum ratio between the host and the emitter material which gives the best exciton transport and recombination. By omitting either the electron or hole blocking layer we prove the favoured electron conductivity of our emission layer. This is shown by strong exciton quenching due to charge carrier accumulation at the interface between hole transport and emission layer. More advantageous is a nearly ambipolar emission system to create a broad light generation zone. We achieve this by including a second doped emission layer (leading to a double emission structure) which has a preferably hole conductive matrix material. This approach enables us to increase the extrapolated device lifetime of similar OLEDs from 100000 hours to 180000 hours with nearly identical efficiencies and operating voltages. This can be explained by reduced number of charge carriers arriving at the blockers.