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Article

Photophysics and Electron Dynamics in Dye-Sensitized Semiconductor Film Studied by Time-Resolved Mid-IR Spectroscopy

Kan Takeshita* and Yutaka Sasaki

Center for Analytical Chemistry and Science, Inc., 1000 Kamoshida-cho, Aoba, Yokohama, 227-0033, Japan

Masahiro Kobashi, Yuki Tanaka, and Shuichi Maeda

Science and Technology Research Center, Mitsubishi Chemical Corporation, 1000 Kamoshida-cho, Aoba, Yokohama, 227-8502, Japan

Akira Yamakata, Taka-aki Ishibashi, and Hiroshi Onishi

Surface Chemistry Laboratory, Kanagawa Academy of Science and Technology (KAST), KSP East 404, 3-2-1 Sakado, Takatsu, Kawasaki 213-0012, Japan

J. Phys. Chem. B, 2003, 107 (17), pp 4156–4161

DOI: 10.1021/jp0275645

Publication Date (Web): April 5, 2003

To whom correspondence should be addressed. E-mail: 5503103@cc. m-kagaku.co.jp. Phone: +81−45−963−3155. Fax: +81−45−963−4261.

Abstract

Photophysics and electron dynamics in dye-sensitized semiconductor film were studied by transient mid-IR spectroscopy, in particular on the nano- to millisecond time scale. As sensitizers, a Ru complex and 9-phynol xanthane derivatives were used. We simultaneously observed electrons injected into the conduction band of a semiconductor and the change of vibration bands due to formation of a cation of a dye molecule. The transient absorption components derived from these two species decayed differently. From this observation, we found that injected electrons decay through two paths; one was back electron transfer, and the other was decay to deep trap sites that cannot be detected by mid-IR light. We could also estimate the amount of electron injection for different dye-sensitized TiO₂. Our transient mid-IR spectroscopy in long time scale introduces a semi-new approach to the slow dynamics in dye-sensitized semiconductors including back electron transfer.

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