X-ray photoelectron spectroscopy has been applied to interface studies of Ag/tris-(8-hydroxyquinoline) aluminum (Alq 3 ) and Ag/LiF/Alq 3 . For Ag/Alq 3 , diffusion of Ag atoms into the Alq 3 layer occurs immediately after the adhesion of the metal onto the organic layer and the process lasts several hours. Insertion of a monolayer-thick LiF buffer at the interface can effectively block the diffusion process. This is quite different from what is observed from Al/LiF/Alq 3 , where Al penetrates into the LiF layer as deep as several nanometers. It is thus concluded that the LiF buffer may play different roles in Ag/LiF/Alq 3 and Al/LiF/Alq 3 and hence different mechanisms may dominate in the two cases for the enhanced carrier injection observed.
- Interfacial diffusion
- Metal/organic interface
- Organic light-emitting device
- X-ray photoelectron spectroscopy