Influence of atmospheric exposure of tris (8-hydroxyquinoline) aluminum (Alq3):: a photoluminescence and absorption study

We have investigated the effects of atmospheric exposure on the properties of tris (8-hydroxyquinoline) aluminum (Alq(3)) thin films by photoluminescence (PL) and UV-Vis absorption measurements. Alq(3) films were evaporated on glass substrates at different temperatures. The influence of annealing on the environmental stability of the films has also been investigated. It has been found that deposition at higher substrate temperature and annealing of the samples deposited at room temperature yield an improvement in the environmental stability of the films, i.e. less decrease in the PL intensity over time with exposure to atmosphere, as well as increased PL intensity. To investigate further the effects of the air exposure, films deposited at room temperature were stored for four days in air, nitrogen, and oxygen. No decrease in PL intensity has been found for storage in nitrogen, while the decrease for the film stored in oxygen was smaller than that for the film stored in air, indicating that both humidity and oxygen play a role in the PL intensity decrease in Alq(3) thin films.