화학공학소재연구정보센터
Current Applied Physics, Vol.4, No.6, 667-670, 2004
Temperature-dependent electrical properties of organic light-emitting diodes depending on cathodes
We have studied temperature-dependent electrical properties of organic light-emitting diodes with a variation of cathode materials; Al, LiAl, and LiF/Al. The organic light-emitting diodes emit a light by a recombination of injected charge carriers such as holes and electrons. Thus, the charge transport is affected by the injection barrier at the interface. By varying the cathode materials, the electron injection at the interface could be controlled because of the work-function change at the cathode. Temperature-dependent current-voltage luminance characteristics of the organic light-emitting diodes were measured in the temperature range from 10 to 300 K. The current-voltage characteristics were analyzed in terms of Fowler-Nordheim tunneling model, and the energy-barrier height was obtained. A measured lifetime of device with LiF/Al cathode is relatively longer than the other cathodes at room temperature: 4.5 h for Al cathode, 12.4 h for LiAl, and 29.6 h for LiF/Al. The device with LiAl and LiF/Al cathode, in the aspect of lifetime and luminous efficiency, is superior to one of other cathodes. (C) 2004 Elsevier B.V. All rights reserved.