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UV Photoemission Study of Interfaces Related to Organic EL Devices

Published online by Cambridge University Press:  10 February 2011

Kiyoshi Sugiyama ,
Kazuhiko Seki ,
Eisuke Ito ,
Yukio Ouchi  and
Hisao ISHII
Kiyoshi Sugiyama
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furocho, Chikusa-ku, Nagoya 464-01, JAPAN, seki@chemI.chem.nagoya-u.ac.jp
Kazuhiko Seki
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furocho, Chikusa-ku, Nagoya 464-01, JAPAN, seki@chemI.chem.nagoya-u.ac.jp
Eisuke Ito
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furocho, Chikusa-ku, Nagoya 464-01, JAPAN, seki@chemI.chem.nagoya-u.ac.jp
Yukio Ouchi
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furocho, Chikusa-ku, Nagoya 464-01, JAPAN, seki@chemI.chem.nagoya-u.ac.jp
Hisao ISHII
Affiliation:
Department of Chemistry, Graduate School of Science, Nagoya University, Furocho, Chikusa-ku, Nagoya 464-01, JAPAN, seki@chemI.chem.nagoya-u.ac.jp
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Abstract

Interfacial electronic structures related to organic electroluminescent (EL) devices were studied by UV photoemission spectroscopy (UPS). The two classes of interfaces studied were: (1) interfaces in a typical multilayer device AI/AIq3TPD/ITO, where Alq3 is tris(8-hydroxyquinolino)- aluminum, TPD is N,N×-diphenyl-NN×-(3-methylphenyl)- 1, 1‘-biphenyl-4,4’-diamine, and ITO is indium tin oxide, and (2) TTN/metals and TCNQ/metals interfaces, where TTN is tetrathianaphthacene and TCNQ is tetracyanoquinodimethane. The UPS studies of the specimen formed by the successive deposition of TPD, Alq3, and Al on ITO revealed interfacial energy diagrams, with the vacuum level shift of - 0.25 eV (downward) and - 0.1 eV (downward) at the TPD / ITO and the Alq3 / TPD interfaces, respectively. The deposition of TTN and TCNQ on metals showed opposite direction of the shift of the vacuum level, with the positive and negative charge at the vacuum side. This can be explained by considering the chargetransfer between the metal and the organic molecule, with these directions being consistent with the electron donating and accepting ability of these molecules.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 488: Symposium J – Electrical, Optical & Magnetic Properties of Organic IV , 1997 , 719
Copyright
Copyright © Materials Research Society 1998

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