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Proceedings Paper

High-efficiency and low-voltage p-i-n electrophosphorescent OLEDs with double-doping emission layers
Author(s): Gufeng He; Desta Gebeyehu; Ansgar G. Werner; Martin Pfeiffer; Karl Leo
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Paper Abstract

We demonstrate high-efficiency organic light-emitting diodes (OLEDs) by incorporating a double emission layer (D-EML) into p-i-n-type cell architecture. The D-EML comprises two layers with ambipolar transport characteristics, both doped with the green phosphorescent dye tris(phenylpyridine)iridium [Ir(ppy)3]. The first EML features a bipolar, but predominantly hole transporting host material, 4,4',4''-tris(N-carbazolyl)-triphenylamine (TCTA), while the second EML is made of an exclusively electron transporting host, e.g. 3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole (TAZ); with a weak hole transport capability arising from hopping between dopant sites. The D-EML system of two bipolar layers leads to an expansion of the exciton generation region. Due to its self-balancing character, it avoids accumulation of charge carriers at any interface. Thus, a power efficiency of approximately 77 lm/W and an external quantum efficiency of 19.3% are achieved at 100 cd/m2 at an operating voltage of only 2.65V. More importantly, the efficiency decays only weakly with increasing brightness and a power efficiency of 50 lm/W is still obtained even at 4,000 cd/m2.

Paper Details

Date Published: 8 September 2004
PDF: 6 pages
Proc. SPIE 5464, Organic Optoelectronics and Photonics, (8 September 2004); doi: 10.1117/12.546729
Show Author Affiliations
Gufeng He, Technische Univ. Dresden (Germany)
Desta Gebeyehu, Technische Univ. Dresden (Germany)
Ansgar G. Werner, Technische Univ. Dresden (Germany)
Martin Pfeiffer, Technische Univ. Dresden (Germany)
Karl Leo, Technische Univ. Dresden (Germany)

Published in SPIE Proceedings Vol. 5464:
Organic Optoelectronics and Photonics
Paul L. Heremans; Michele Muccini; Hans Hofstraat, Editor(s)

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