Berlin 2005 – wissenschaftliches Programm
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SYOO: Organic Optoelectronics and Photonics
SYOO 5: Optoelectronic Devices
SYOO 5.1: Vortrag
Montag, 7. März 2005, 17:15–17:30, TU HE101
APPROACHING THE QUANTUM LIMIT WITH POLYMER ELECTROPHOSPHORESCENT DEVICES — •D. Neher1, X.H. Yang1, Th. Däubler2, N. Reckfuss3, D. Müller3, and K. Meerholz3 — 1Institute of Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam — 2Schott AG, Hattenbergstrasse 10, 55122 Mainz — 3Institute of Physical Chemistry, University of Köln, Luxemburger Str. 116, 50939 Köln
Until very recently, the quantum efficiencies of polymer-based electrophosphorescent LEDs lacked well behind those of corresponding small-molecule LEDs. Here, we demonstrate that by (a) choosing appropriate preparation conditions of the active layer, (b) optimizing charge injection and (c) confining the charge carrier recombination zone, highly efficient dye-doped polymer electrophosphorescent devices can be achieved. With commercially available Ir-dyes, peak external quantum efficiencies are 19 % for green-emitting and 13 % for red-emitting phosphors. These values are comparable to the best efficiencies achieved with small molecule devices. Also, processes limiting the EQE in blue-emitting phosphorescent diodes based on PVK are evaluated with respect to triplet-confinement and exciton back transfer processes.
(1) X.H. Yang, D. Neher, D. Hertel, Th.K. Däubler, Adv. Mater. 16 (2004) 161.
(2) X.H. Yang, D. Neher, Appl. Phys. Lett. 84 (2004) 2476.