Dresden 2006 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 23: POSTER Functional Organic Thin Films

CPP 23.33: Poster

Thursday, March 30, 2006, 17:00–19:00, P2

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

A way to reach highly efficient red bottom emission OLEDs is the use of doped transport layers and phosphorescent emitter materials for high quantum yield. We will show how the efficiency of such devices can be further increased. The p-i-n devices consist of doped transport layers, charge and exciton blockers, and a dilute emitter substance within an appropriate emitter matrix. Most advantageous for high efficiency is a nearly ambipolar emission system to create a broad light generation zone. Therefore, the favoured charge carrier type of different emission layers was studied. By combining preferably electron and hole conducting hosts, doped with the same triplet emitter dye, we reach a well-balanced emission layer (leading to a double emission layer structure) where the charge recombination occurs mainly close to the interface of both emission layer. This approach enables us to increase the 100 cd/m2 efficiency from 9,3 cd/A to 11,2 cd/A with a high device stability of more than 50.000 hours lifetime. Both can be explained by reduced number of charge carriers leaking to the opposite blocking layers and less exciton-exciton quenching due to a reduced charge and exciton accumulation.