AVS 45th International Symposium
    Organic Electronic Materials Topical Conference Tuesday Sessions
       Session OE+AS+EM-TuM

Paper OE+AS+EM-TuM4
Interface Dipoles and Band Bending in Organic Semiconductor Interfaces

Tuesday, November 3, 1998, 9:20 am, Room 327

Session: Organic Thin Film Interfaces
Presenter: R. Schlaf, Colorado State University
Authors: R. Schlaf, Colorado State University
M.W. Nelson, Colorado State University
P.G. Schroeder, Colorado State University
B.A. Parkinson, Colorado State University
P.A. Lee, University of Arizona
K.W. Nebesny, University of Arizona
N.R. Armstrong, University of Arizona
Correspondent: Click to Email
The fast paced development in the field of organic light emitting diodes (OLED) and thin film transistors (OTFT) has sparked intense efforts to determine the electronic structure at organic interfaces and to understand the rules governing it. Photoemission spectroscopy (PES) measurements offer direct information about the HOMO alignment, interface dipole and band bending at such interfaces. We performed multistep growth experiments with insitu PES characterization on a variety of organic/organic, organic/inorganic semiconductor and organic/conductor interfaces. We used combined X-ray and UV photoemission spectroscopies (XPS, UPS) which allow the separate determination of the band bending across the interface. This procedure, which is well established in the field of inorganic semiconductor heterojunctions, allows the measurement of HOMO alignment and interface dipoles with high precision. High precision results from avoiding the problem of the superposition of substrate and overlayer emissions in UP-spectra where elaborate curve fitting procedures are needed to distinguish between band bending and HOMO alignment. Our measurements indicate that band bending and interface dipoles play a significant role in the electronic structure at these interfaces similar to effects known from inorganic semiconductor interfaces. The interface dipoles are discussed in terms of quantum and structural dipoles caused by tunneling of charge carriers and permanent molecular dipoles at the interface.