Regensburg 2004 – wissenschaftliches Programm

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SYOH: Organic and Hybrid Systems for Future Electronics

SYOH 5: Poster

SYOH 5.78: Poster

Donnerstag, 11. März 2004, 18:00–21:00, B

High Efficiency and Low Voltage p-i-n Electrophosphorescent OLEDs with Double Emission Layer — •Gufeng He, Martin Pfeiffer, and Karl Leo — Institut fuer Angewandte Photophysik, Technische Universitaet Dresden, D-01062 Dresden,Germany

We demonstrate high-efficiency and low-voltage organic phosphorescent light-emitting devices employing a green phosphor, tris(2-phenylpyridine) iridium [Ir(ppy)3].

The intrinsic emitting layers are sandwiched between two p- and n-doped layers. The p-i-n structure results in efficient carrier-injection from both contacts into the doped transport layers and low ohmic losses. Thus, low operating voltages are obtained compared to conventional undoped OLEDs.

By doping Ir(ppy)3 into both electron- and hole-transport hosts, a power efficiency of 70 lm/W and external quantum efficiency of 19.5 at 100 cd/m2 (2.95V). More importantly, the efficiency decays only weakly with increasing current density (or brightness). A quantum efficiency of 13.5 luminance of around 50,000 cd/m2. This improvement can be attributed mainly to the confinement of the recombination region to the interface of the dye doped electron- and hole-transport hosts. Thus, the influence of electron or blocking layers is reduced as compared to conventional single-emission-layer structures and charge accumulation at the interfaces of these blocking layers is avoided.