Hole-Exciton Interaction Induced High Field Decay Of Magneto-Electroluminescence In Alq(3)-Based Organic Light-Emitting Diodes At Room Temperature

The magnetic field effects on the electroluminescence of aluminium tris-(8-hydroxyqinoline) (Alq(3)) based organic light emitting diodes have been investigated by varying the electron/hole ratio in the emissive layer. Experimental results reveal that a negative high field effect in the magnetoelectroluminescence (MEL) can be found in devices with very low triplet exciton concentration at room temperature. This suggests triplet-triplet annihilation cannot be used to explain the negative high field MEL in the Alq(3) system. Our results suggest that hole-exciton interaction may be the origin of the negative high field MEL and also, in parallel with this interaction, there is also the more common positive high field process occurring which has been tentatively attributed to electronexciton interactions. The competition between these different processes decides the final shape of the MEL at high fields. (C) 2016 AIP Publishing LLC.