Andronique Ioannidis

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.

Time-resolved fluorescence studies of degradation in tris(8-hydroxyquinoline) aluminum (AlQ3)-based organic light emitting devices (OLEDs)

Abstract Device stability has been a major concern for organic light emitting devices (OLEDs). Recently, we found that the injection of holes in tris(8-hydroxyquinoline) aluminum (AlQ3), a widely used organic electroluminescent material, is the main factor responsible for degradation in OLEDs based on this material. The photoluminescence (PL) quantum efficiency of AlQ3 has been found to decrease as a result of predominantly hole current flow. Studies using time-resolved fluorescence measurements show that the decrease in the PL quantum efficiency is associated with a decrease in the lifetime of the AlQ3 excited states, thus revealing the nature of the degradation products as luminescence quenchers.

Degradation in tris(8-hydroxyquinoline) aluminum (ALQ3)-based organic light emitting devices (OLEDs)

Poor device stability has been a major concern for organic light emitting devices (OLEDs). The relatively short operational lifetime of the OLEDs is predominantly attributed to an intrinsic degradation behavior, which leads to a decrease in the electroluminescence quantum efficiency of the devices in time. Recently, we found that the injection of holes in tris(8-hydroxyquinoline) aluminum (AlQ3), the most widely used organic electroluminescent material, is the main factor responsible for the intrinsic degradation behavior in OLEDs. The photoluminescence quantum efficiency of AlQ3 has been found to decrease as a result of predominantly hole current flow. Further studies using time-resolved fluorescence measurements reveal that degradation is also associated with a decrease in the lifetime of the AlQ3 excited states, thus revealing the nature of the degradation products as luminescence quenchers. Various phenomena pertaining to device degradation will be discussed.