Dresden 2009 – scientific programme

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DS: Fachverband Dünne Schichten

DS 16: Poster I

DS 16.11: Poster

Tuesday, March 24, 2009, 09:30–12:30, P5

Top emitting white OLEDs — Patricia Freitag, Björn Lüssem, and •Karl Leo — Technische Universität Dresden, Institut für Angewandte Photophysik, George-Bähr-Strasse 1, 01069 Dresden, Germany

Top emitting organic light emitting diodes (TOLEDs) provide a number of interesting opportunities for new applications, such as the opportunity to fabricate ITO-free devices by using opaque substrates. This makes it possible to manufacture low cost OLEDs for signage and lighting applications.

A general top emitting device consists of highly reflecting metal contacts as anode and semitransparent cathode, the latter one for better outcouling reasons. In between several organic materials are deposited as charge transporting, blocking, and emission layers.

Here, we show a top emitting white organic light emitting diode with silver electrodes arranged in a p-i-n structure with p- and n-doped charge transport layers. The centrical emission layer consists of two phosphorescent (red and green) and one fluorescent (blue) emitter systems separated by an ambipolar interlayer to avoid mutual exciton quenching.

By adding an additional dielectric capping layer on top of the device stack, we achieve a reduction of the strong microcavity effects which appear due to the high reflection of both metal electrodes. Therefore, the outcoupled light shows broad and nearly angle-independent emission spectra, which is essential for white light emitting diodes.