Regensburg 2013 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Poster: Organic Semiconductors
CPP 32.12: Poster
Mittwoch, 13. März 2013, 16:30–18:30, Poster C
Optoelectronic Processes in Squaraine Dye-Doped OLEDs for Emission in the Near-Infrared — •B. Stender1, S. F. Völker2, C. Lambert2, and J. Pflaum1,3 — 1Experimental Physics VI, University of Würzburg, D-97074 Würzburg — 2Institute of Organic Chemistry and Center for Nanosystems Chemistry, University of Würzburg, D-97074 Würzburg — 3ZAE Bayern, D-97074 Würzburg
Organic light-emitting diodes (OLEDs) for emission in the near-infrared (NIR) offer the great advantage of room temperature operation due to inherently high exciton binding energies (several 100 meV) in contrast to their inorganic counterparts. Despite several approaches have been presented with reasonable efficiency, purely organic NIR-emitters are barely investigated due to degradation of the organic compound. To cope with this challenge a novel organic host-guest system consisting of the polymer SY-PPV and the squaraine dye monomer M has been investigated. Optical excitation reveals a highly efficient energy transfer from the visible range to the NIR (750 nm) with a doping concentration of less than 2.0 wt.% and an associated Förster radius of 3.8 nm. As will be demonstrated, electrically driven NIR-emission yields an efficiency of 0.65% at a current density of 2.26 mA/cm2 with a turn-on voltage of 2.0 V at a doping concentration of only 0.05 wt.%. Comparison between steady-state photo- and electroluminescence provides access to the opto-electronic processes on molecular length scales, thereby indicating that NIR-OLED emission in this system is controlled by charge carrier dynamics rather than by exciton transfer.