IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Organic Films and Devices Thursday Sessions
       Session OF+EL+TF-ThA

Paper OF+EL+TF-ThA8
The Electronic Structure Studies of Fluoride Layer Insertion between Al and Organic EL Material@footnote 1@

Thursday, November 1, 2001, 4:20 pm, Room 131

Session: Electronic Properties of Organic Thin Films
Presenter: Y. Park, Korea Research Institute of Standards and Science
Authors: Y. Park, Korea Research Institute of Standards and Science
J. Lee, Korea Research Institute of Standards and Science
D.Y. Kim, Hallym University, Korea
S.K. Lee, Chonnam University, Korea
Correspondent: Click to Email
We have investigated the electronic structures of interfaces between Al and tris-(8-hydroxyquinoline)aluminum (Alq@sub 3@), which is a prototypical organic electroluminescent (EL) material. It has been well known that the insertion of alkali metal fluoride, such as LiF, greatly enhances the EL performance and the origin of such behaviors have been controversial. We used photoelectron spectroscopy techniques including X-ray and UV photoelectron spectroscopy (XPS and UPS) to probe the electronic structures of Al/fluorides/Alq@sub 3@ interfaces. While the presence of LiF layer exhibited enhanced gap states and concomitant formation of shoulder peak in N 1s core level peaks, insertion of other fluorides showed distinctively different behaviors. For example, the presence of MgF@sub 2@ does not form N 1s shoulder peak although weak gap states were observed. Other fluorides including CsF and CaF@sub 2@ are also studied. In addition, the mixture of Al, LiF, and AlF@sub 3@ sequentially deposited on Alq@sub 3@ were investigated. The various core level peaks in this system revealed that this combination does not distinguish LiF and AlF@sub 3@, rather it is more like a homogeneous mixture of LiF, AlF@sub 3@ and Al, which is in contrast to the view that the deposition of Al on LiF/Alq@sub 3@ forms AlF@sub 3@ and liberated Li. We discuss the implications of these results in the electrical properties of the interface and eventually the organic ELD performance that employs this type of electrodes. @FootnoteText@ @footnote 1@ This work was supported in part by MOST of Korea through NRL Program and ASSRC.