Dresden 2011 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 32: Spins in Organic Materials III (Focused Session, jointly with MA -- Organisers: Salvan, Hess, Timm)

DS 32.6: Vortrag

Mittwoch, 16. März 2011, 18:15–18:30, GER 37

Degradation effect on the magnetoresistance in organic light emitting diodes — •Andreas Buchschuster, Tobias Schmidt, and Wolfgang Brütting — Institute of Physics, University of Augsburg, 86135 Augsburg, Germany

The effect of a magnetic field on the resistance and the luminance of organic light emitting diodes (OLEDs) is commonly observed but not yet fully understood. One of the recent findings was that the magnetic field effect on the resistance (OMR) as well as the effect on the luminance (OML) can be enhanced drastically by electrical stressing of the device.

To investigate both phenomena we studied OLEDs based on small molecules with tris(8-hydroxyquinoline)aluminium (Alq₃) as emitting material. Measurements were performed on two different types of hetero-layer devices which only differed in their hole injection layer (HIL) whereat one of the devices exhibited a significantly longer lifetime. Magnetic field effects on the current and the luminance have been detected up to 100 mT while the stressing time was 500 h at the most. We found values up to 5.6 % for the OMR and about 9 % for the OML as well as a correlation of both effects with the degradation of the device. As a result we could show that the transport properties of the hole injection layer has a strong influence on the magnetic field effects.