Simultaneous electroluminescence and photoluminescence aging studies of tris(8-hydroxyquinoline) aluminum-based organic light-emitting devices

Using experimental devices which do not show electroluminescence, we have previously found that photoluminescence of tris(8-hydroxyquinoline) aluminum (AlQ3), a widely used organic electroluminescent material, decreases under prolonged transport of holes. This leads to a conclusion that AlQ3 cations are unstable, and to our proposal that the same mechanism is responsible for degradation of organic light-emitting devices (OLEDs) based on AlQ3. In this communication, we broaden our studies to include simultaneous electroluminescence and photoluminescence measurements on OLEDs containing thin AlQ3 as the emitter layer. Results show that the decrease in the electroluminescence efficiency is indeed associated with degradation of the AlQ3 in the vicinity of the hole transport layer interface.