Temperature dependence of electroluminescence degradation in organic light emitting devices without and with a copper phthalocyanine buffer layer

Temperature dependence of electroluminescence degradation was investigated in two types of organic light emitting devices (OLEDs) based on tris(8-hydroxyquinoline) aluminum (AlQ(3)) emitter molecule, one without and another with copper phthalocyanine (CuPc) buffer layer at the hole-injecting contact interface. Electroluminescence degradation in time was measured for devices operated at 22 and 70 degreesC. Results unexpectedly showed that devices without the CuPc buffer layer demonstrated negligible change in half-life when operated at 22 or 70 degreesC, while devices with the CuPc layer showed the expected decrease in half-life when the temperature was increased. The results are explained within the framework of recently proposed OLED degradation mechanism, which identifies AlQ(3) cations as unstable, leading to device degradation. (C) 2002 Elsevier Science B.V. All rights reserved.