Hamburg 2001 – scientific programme
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SYOF: Organische Festkörper
SYOF 1: Organic Semiconductor Devices
SYOF 1.3: Talk
Tuesday, March 27, 2001, 10:25–10:40, S6
Emissive and non-emissive dopants in polyfluorene emission layers — •Dieter Neher1, Dessislava Sainova1, Andreas Meisel2, Tzenka Miteva3, Heinz-Georg Nothofer2, Andreas Herrmann2, Klaus Muellen2, Ewa Dobruchowska4, Irek Glowacki4, Jacek Ulanski4, and Ullrich Scherf5 — 1University of Potsdam, Inst. Physics, Am Neuen Palais 10, 14469 Potsdam — 2MPI for Polymer Reseach, Ackermannweg 10, 55128 Mainz — 3Sony International (Europe), MSL, Hedelfinger Strasse 61, 70327 Stuttgart — 4Technical University of Lodz, 90-924 Lodz, Polen — 5University of Potsdam, Inst. Phys. Chem. und Theor. Chem, Karl-Liebknecht-Str. 24-25, 14476 Golm
The emission properties of light-emitting diodes (LEDs) based on polyfluorene (PF) emission layers can be significantly altered by adding emissive or non-emissive molecules with appropriate energy levels. Using hole-transporting molecules (HTM) with low oxidation potentials, a significant improvement in efficiency, accompanied by improved color stability is achieved. Based on investigations on hole-only devices and thermally-stimulated luminescence (TL) measurements, the effect can be attributed to hole trapping. Investigations on LEDs, containing emissive perylene dendrimers in in the PF emission layer give strong evidence, that charge carrier trapping rather than energy transfer processes governs the emission properties in these layers. In particular, pronounced voltage-controlled color tuning is observed for dendrimers with appropriate thickness of the isolating scaffold.