Low temperature magnetic field effects on the efficiency of aluminium tris(8-hydroxyquinoline) based organic light emitting diodes in the absence of magnetoresistance

• Published in: Synthetic metals Vol. 173; pp. 46 - 50
• Main Authors: Zhang, Sijie, Kreouzis, T., Gillin, W.P.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01-06-2013; Elsevier
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Optoelectronic devices; Organic magnetoresistance; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Organic magnetoresistance; Magnetic field effect; Charge carrier trapping; Triplet triplet annihilation; Tunnel effect; Quinoline derivatives; Temperature effect; Aluminium compound; Light emitting diode
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/j.synthmet.2012.11.016

► We studied low temperature organic magnetoresistance measurements. ► We observed changes in efficiency where no change in current was found. ► TTA was found to correlate to a non-linearity in the OMR with light output.
This paper presents low temperature results of the magnetic field effect on current and efficiency in Alq3 based light emitting diodes (OLEDs). We report a magnetic field effect on light output at driving voltages where no magnetic effect is measured on the current. This is attributed to the presence of significant trapping, where trapped carriers are unable to de-trap at low temperature. At high current densities and corresponding bias, magnetoresistance is observed as a result of trap filling or field assisted tunnelling. A negative magnetic field effect (MFE) on efficiency at low temperatures and a deviation from the linear relationship between organic magnetoresistance (OMR) and singlet population are also observed. The latter are attributed to significant triplet–triplet annihilation (TTA) occurring within the device.