Effects of Chemical and Physical Agents on the Emission Properties of Alq[sub 3] Films

Abstract

Tris(8-hydroxyquinoline)aluminum (Alq 3 )-based organic light emitting diodes are highly susceptible to environmental conditions which severely limit their lifetime. In particular, moisture and oxygen play an important role in the degradation processes. In order to study those effects more deeply, annealing processes of Alq 3 films have been performed in various atmospheres, and they have confirmed the physical and chemical destructive actions of temperature, oxygen, and water, the last one more effective than the previous two agents. However, also a sizeable increase of the photoluminescence has been discovered by annealing in humidified atmospheres, especially air. Due to the complexity of the matter, it is not yet clear whether this important effect can be ascribed to the temperature alone or to the combined action of temperature and water, but almost certainly it is related to the phase transitions of the molecular material itself.