Berlin 2005 – scientific programme
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SYOO: Organic Optoelectronics and Photonics
SYOO 6: Poster
SYOO 6.2: Poster
Monday, March 7, 2005, 18:00–20:00, Poster TU A
Organic p-i-n homojunctions: Fundamental properties and application in red phosphorescent OLED — •Kentaro Harada1, Ansgar G. Werner2, Olaf Kühl1, Martin Pfeiffer1, and Karl Leo1 — 1Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden, Germany — 2Novaled GmbH, Zellescher Weg 17, D-01069 Dresden, Germany
Organic light emitting diodes (OLEDs) have been currently broadly studied, and it has been shown that efficient luminescence can be achieved by heterostructures utilizing suitable organic materials as the charge transport and blocking layers. Recently, we have realized the first example of a stable and reproducible organic p-i-n homojunction using a phthalocyanine as the matrix. Here, the main challenge was the simultaneous n- and p-type doping of the same material. Using strong organic acceptors like perfluorinated tetracyanoquinodimethane(TCNQ) and metal-organic donors synthesized and handled in strict absence of oxygen, we show that several organic matrices can form p-i-n homojunctions with high built-in potentials: Using a porphyrine as the matrix, a built-in potential of around 1.2 V is achieved. The homojunctions show well-behaved diode characteristics with rectification ratios up to 105. A homojunction composed of a phosphorescent metal-complex emits fairly intense red light under forward bias. We discuss the properties of these archetypal homojunction OLEDs with respect to the luminescence efficiency and current-voltage characteristics and compare the results with optimized heterostructure OLEDs.