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Proceedings Paper

Evidence of electron and hole transfer in metal/CuPc interfaces
Author(s): Neil J. Watkins; Li Yan; Serkan Zorba; Yongli Gao; Ching W. Tang
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Paper Abstract

The electronic structures of interfaces between metals and Copper phthalocyanine (CuPc) organic films are investigated using the combination of ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPES). The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) can be directly observed by IPES and UPS simultaneously. We found that the Fermi level, EF, in the organic film can be modified by metals through charge transfer or doping. The FERMI level at the Cs/CuPc interface is observed to shift to less than 0.2 eV below the CuPc LUMO. The IPES observation is the first direct confirmation of Fermi level pinning near the LUMO in organic films. The pinning of the Fermi level close to the LUMO can be explained by electron transfer from Cs to CuPc, which is supported by the presence of a gap state in CuPc as observed with UPS. On the other hand, the Au/CuPc interface is characterized by electron transfer from CuPc to Au, resulting in a reduced HOMO intensity shown in the UPS spectra and a new feature below the LUMO shown in the IPES spectra. These observations shed new light onto the understanding of interface formation in organic semiconductor devices.

Paper Details

Date Published: 3 March 2003
PDF: 8 pages
Proc. SPIE 4800, Organic Light-Emitting Materials and Devices VI, (3 March 2003); doi: 10.1117/12.453254
Show Author Affiliations
Neil J. Watkins, Univ. of Rochester (United States)
Li Yan, Univ. of Rochester (United States)
Serkan Zorba, Univ. of Rochester (United States)
Yongli Gao, Univ. of Rochester (United States)
Ching W. Tang, Eastman Kodak Co. (United States)

Published in SPIE Proceedings Vol. 4800:
Organic Light-Emitting Materials and Devices VI
Zakya H. Kafafi; Homer Antoniadis, Editor(s)

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