Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 23: POSTER Functional Organic Thin Films
CPP 23.32: Poster
Thursday, March 30, 2006, 17:00–19:00, P2
High efficiency white organic light emitting devices combining fluorescent and phosphorescent emitter systems — •Gregor Schwartz, Karsten Walzer, Martin Pfeiffer, and Karl Leo — Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden
Light sources suitable for lighting applications need to combine high power efficiency at high brightness, good color rendering as well as color coordinates matching those of the standard reference illuminants. We demonstrate white organic light emitting devices (WOLED) combining a blue fluorescent dye with red and green Iridium based phosphorescent dopants in separate host materials. The devices are competitive with the best reported ones based on three phosphorescent emitters. In our WOLEDs, we could simultaneously achieve a power efficiency of 13.7lm/W at a brightness of 1000cd/m2, a color rendering index of 85 and color coordinates of (0.47/0.42), which is a color very close to the standard warm white illuminant A. Crucial features of the devices are the use of electrically doped transport layers (p-i-n concept) which leads to low driving voltages, and a thin additional layer separating the fluorescent dye from the two phosphorescent emitter systems to prevent Dexter type quenching of the phosphorescent emission. We studied the influence of thickness and doping ratio of the different layers on the electroluminescence spectrum and on the current-voltage characteristics to understand the charge carrier balance and mechanisms of exciton generation inside the devices.