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SYOF: Organische Festkörper

SYOF 5: Poster Session

SYOF 5.38: Poster

Dienstag, 27. März 2001, 17:00–19:00, Aula S3

Low voltage organic light-emitting diodes by doped amorphous hole transport layers — •Jan Blochwitz, Martin Pfeiffer, Xiang Zhou, Ansgar Werner, Andreas Nollau, and Karl Leo — Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden, www.iapp.de

Inorganic light emitting diodes usually have a nominal operating voltage close to the thermodynamic limit, i.e., the operating voltage is about the band gap divided by the elementary charge. For polymer OLED, such values have been almost reached (2.6V for 100 cd/m², CDT) for very thin devices and metal contacts with very low work function. For small molecule devices, the operating voltages have been usually quite higher, with the lowest voltages reported to our knowledge by Kido et al. (4 V for 100 cd/m²). Here, we demonstrate that a typical amorphous hole transport material for OLEDs can be doped very well and allows to realize highly efficient devices with very low operating voltage, even for comparatively thick. We present results for a amorphous starburst amine (TDATA), doped with a very strong acceptor, tetrafluoro-tetracyano-quinodimethane (F4-TCNQ) by controlled coevaporation. Multilayered OLEDs consisting of double hole transport layers of p-doped TDATA and triphenyldiamine (TPD), and an emitting layer of pure Alq3 very low operating voltage (3.1 V for 100 cd/m²), although we use a comparatively large (110 nm) total hole transport layer thickness.