Influence of aging treatment on magneto-electroluminescence in organic light emitting diodes

We investigated the influence of electric stress condition on organic magneto-electroluminescence(MEL) in tri-(8-hydroxyquinoline)aluminum(Alq3)-based organic light-emitting diodes.The results show that the performance of the devices goes to bad as increasing the aging time;in particular,the threshold voltage becomes larger and the luminescence efficiency gets lower.Moreover,the magnitude of the MEL increases firstly and then gets smaller with the line shape unchanged as the device aging.Possible explanations for the above effects were proposed based on the mechanism of the device aging.We suggested that the quencher,Alq3 cation-radicals,which formed in the emitting layer,reduce the EL intensity and enhance the magnitude of MEL.In addition,the increase in turn-on voltage and the decrease in MEL are assigned to the degradation at the interface of Al/Alq3.