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Electronic Structure of Ionic Liquids Studied by UV Photoemission and Inverse Photoemission Spectroscopy

Published online by Cambridge University Press:  26 February 2011

Toshio Nishi ,
Yasunori Kamizuru ,
Kaname Kanai ,
Yukio Ouchi  and
Kazuhiko Seki
Toshio Nishi
Affiliation:
toshio@mat.chem.nagoya-u.ac.jp, Nagoya University, Department of Chemistry, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan, 052-789-2945, 052-789-2944
Yasunori Kamizuru
Affiliation:
kamizuru@mat.chem.nagoya-u.ac.jp, Nagoya University, Department of Chemistry, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
Kaname Kanai
Affiliation:
kaname@mat.chem.nagoya-u.ac.jp, Nagoya University, Department of Chemistry, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
Yukio Ouchi
Affiliation:
ohuchi@mat.chem.nagoya-u.ac.jp, Nagoya University, Department of Chemistry, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
Kazuhiko Seki
Affiliation:
seki@mat.chem.nagoya-u.ac.jp, Nagoya University, Department of Chemistry, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
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Abstract

Electronic structures of the ionic liquids were studied by ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPES). The sample materials contain 1-buthyl-3-alkylimidazolium ion [Cnmim]+ (n=4, 8, 10) as the cation in combination with fluorine-containing anions (tetrafluoroboronate BF4−, hexafluorophosphate PF6−). Comparing the calculated density of states with the observed spectra, we found that the ionization thresholds of these ionic liquids are determined by the highest occupied molecular orbitals (HOMO) of the cation, although the calculated HOMOs of the isolated anions are higher than that of isolated cation. The combination of the UPS and IPES results reveals that the band gaps of these ionic liquids are determined by only cation.

Keywords

electronic structureorganicphotoemission
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 965: Symposium S – Organic Electronics – Materials, Devices and Applications , 2006 , 0965-S13-10
Copyright
Copyright © Materials Research Society 2007

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