Modelling of organic magnetoresistance as a function of temperature using the triplet polaron interaction

The organic magnetoresistance (OMR) of 50 nm aluminium tris(8-hydroxyquinoline) organic light emitting diodes (OLEDs) has been measured over a range of temperatures and operating voltages. The OMR data for this device, the current change through the device with applied field, have been fitted using the triplet polaron interaction (TPI) model that includes two independent processes, namely the exciton trapping and the triplet polaron interaction. Two Lorentzian functions were used to fit the data, and the prefactors for the two processes were found to scale linearly with the triplet population. Over the whole temperature range the data appears to fall on a single line which covers nearly six orders of magnitude of exciton concentration. This work demonstrates that the magnitude and shape of the OMR can be predicted and will be useful for understanding the fundamental mechanism behind the OMR.