Dongge Ma et al 2002 J. Phys. D: Appl. Phys. 35 520 doi:10.1088/0022-3727/35/6/305
Dongge Ma1,3, J M Lupton1, R Beavington2, P L Burn2 and I D W Samuel1
Show affiliationsIn this paper, we study the effects of electrical annealing at different voltages on the performance of organic light-emitting diodes. The light-emitting diodes studied here are single-layer devices based on a conjugated dendrimer doped with 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as the emissive layer. We find that these devices can be annealed electrically by applying a voltage. This process reduces the turn-on voltage and enhances the brightness and efficiency. We obtained an external electroluminescence quantum efficiency of 0.07% photon/electron and a brightness of 2900 cd m-2 after 12.4 V electrical annealing, which are about 6 times and 9 times higher than un-annealing devices, respectively. The improved luminance and efficiency are attributed to the presence of a space charge field near the electrodes caused by charging of traps.
85.60.Jb Light-emitting devices
Condensed matter: electrical, magnetic and optical
Issue 6 (21 March 2002)
Received 7 September 2001, in final form 14 November 2001
Published 5 March 2002
Dongge Ma et al 2002 J. Phys. D: Appl. Phys. 35 520
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