Time-resolved study of the magnetic field effects on electroluminescence in tri-(8-hydroxyquinoline)- aluminum based organic light emitting devices

We investigated the magnetic field effects (MFEs) in organic light-emitting diodes (OLEDs) through the transient electroluminescence (EL) method. The time-resolved MFEs on the emission were obtained for the first time, which would be a useful method to clarify the underlying mechanisms of the MFEs. The fluorescent dye doped tri-(8-hydroxyquinoline)-aluminum (Alq3) based OLEDs were fabricated. Then, the transient EL was measured both with and without a magnetic field. To explore the time-resolved MFEs on the emission of the device, the excitons population dynamics in the device have been analyzed by a kinetic model. Our results suggest that both the intersystem crossing between the singlet and triplet electron-hole pairs and the triplet-triplet annihilation perturbed by the external magnetic field cause the time-resolved MFEs.