AVS 46th International Symposium
    Organic Electronic Materials Topical Conference Tuesday Sessions
       Session OE+EM+AS-TuM

Invited Paper OE+EM+AS-TuM1
Electronic Properties of Organic Semiconductor Interfaces

Tuesday, October 26, 1999, 8:20 am, Room 616/617

Session: Interfaces and Characterization of Organic Thin Films
Presenter: I.G. Hill, Princeton University
Authors: I.G. Hill, Princeton University
C. Shen, Princeton University
D. Markiewicz, Princeton University
J. Schwartz, Princeton University
A. Kahn, Princeton University
Correspondent: Click to Email
The alignment of molecular energy levels at the interfaces of organic semiconductor films plays a critical role in determining organic light emitting device (OLED) efficiencies. At a metal/semiconductor interface, the positions of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO respectively) relative to the metal Fermi level determine the barriers for charge injection into the organic. At organic/organic heterointerfaces, the relative alignment of the HOMO and LUMO levels of the two organics determines whether charges will flow freely across the interface or result in charge accumulation. It is now widely accepted that vacuum levels do not, in general, align at metal/organic interfaces,@footnote 1,2@ implying that techniques such as ultraviolet photoelectron spectroscopy (UPS) and internal photoemission must be used to determine barrier heights. Vacuum levels do align at the majority of organic/organic heterointerfaces, with a few notable exceptions.@footnote 3@ Using UPS, we have studied a variety of both metal/organic and organic/organic interfaces with the goal of understanding the origin of, and therefore ways to control, the interface dipoles which result in vacuum level discontinuities. The results of these studies will be discussed with an emphasis on our attempts to understand the roles of surface modifying procedures, such as oxygen plasma treatment of indium tin oxide (ITO), on improving device performance. @FootnoteText@ @footnote 1@H. Ishii and K. Seki, IEEE Trans. Electr. Devices 44, 1295, (1997) @footnote 2@I.G. Hill, A. Rajagopal and A. Kahn, Appl. Phys. Lett., 73, 662, (1998). @footnote 3@I.G. Hill and A. Kahn, Proceedings of SPIE, Organic Light-Emitting Materials and Devices II, 3476, 168, (1998).