Long-term degradation mechanism of tris(8 -hydroxyquinoline)aluminum-based organic light-emitting devices

摘要

We investigated the cause of the long-term degradation of organic light-emitting devices (OLED) based on tris(8-hydroxyquinoline) aluminum (AlQ_3), a widely used electroluminescent small molecule. We found that injection of holes in AlQ_3 is the main factor responsible for device degradation. This was verified by constructing devices where predominantly holes were transported through a 5-nm-thick AlQ_3 layer. These devices showed a significant decrease in the photoluminescence efficiency upon prolonged current flow, showing that AlQ_3 cations are unstable and their degradation products are fluorescence quenchers. This fact naturally explains various approaches, which have been used previously to increase OLED lifetime.