Improving the performance of organic light-emitting diodes containing BCP/LiF/Al by thermal annealing

In this paper, we examined the effect of post-packaging annealing on the performance of organic light-emitting diodes containing tris-(S-hydroxyquinoline) aluminum (Alq₃) or 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) in direct contact with a LiF-Al bilayer cathode. The detailed electroluminescent (EL) characteristics were compared before and after annealing at 70°C for 5 hrs. It was found that better luminous efficiency as well as greater power efficiency could be achieved for devices with BCP/LiF/Al structure. However, other devices consisting of Alq₃/LiF/Al were less affected. It is believed that the thermal treatment helps to enhance the electron injection for the former, and less helpful for the latter.