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Proceedings Paper

Time-resolved photoelectrochemical measurements and photovoltaic efficiency of electrochemically self-assembled ZnO-dye electrodes
Author(s): Derck Schlettwein; Torsten Oekermann; Yoshida Tsukasa; Takashi Sugiura; Hideki Minoura; Dieter Woehrle
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Paper Abstract

Dye-modified ZnO thin films were prepared by electrochemically induced crystallization from aqueous mixtures of zinc nitrate and water-soluble dyes. A direct crystallization of semiconductor/ dye composites without heat treatment is seen as a significant advantage of this method. Moreover, characterization of these materials has revealed ordered growth of ZnO crystallites as well as formation of ordered dye assemblies, thus characterizing this method as electrochemical self-assembly. The photoelectrochemical properties of these unique ZnO-dye thin film electrodes were investigated in photocurrent transient measurements in the ms-regime and by steady- state voltammetric measurements. Two sets of electrodes are discussed, employing either metal complexes of tetrasulfophthalocyanines (TSPcMt; Mt = Zn, Al, Si) or the xanthene dye Eosin Y. For aggregates of TSPcMt on ZnO, efficient charge-transfer to the electrolyte is found, leading to low surface charging and low surface recombination of photogenerated holes with electrons from the ZnO, at however, rather low injection efficiencies of electrons into the conduction band of ZnO. This efficiency was higher for adsorbed monomers of TSPcMt leading to a considerably higher quantum efficiency of the photocurrent in spite of increased surface charging and recombination of holes. Higher photocurrents were observed for ZnO sensitized with monomers of Eosin Y caused by both, efficient electron transfer from the dye to ZnO as well as hole transfer from the dye to the electrolyte. Not only dye molecules which were directly accessible from the electrolyte, but also those which were enclosed within matrix cavities proved to be photoelectrochemically active.

Paper Details

Date Published: 21 February 2002
PDF: 9 pages
Proc. SPIE 4465, Organic Photovoltaics II, (21 February 2002); doi: 10.1117/12.456926
Show Author Affiliations
Derck Schlettwein, Univ. Bremen and Univ. Oldenburg (Germany)
Torsten Oekermann, Univ. Bremen and Gifu Univ. (Germany)
Yoshida Tsukasa, Gifu Univ. (Japan)
Takashi Sugiura, Gifu Univ. (Japan)
Hideki Minoura, Gifu Univ. (Japan)
Dieter Woehrle, Univ. Bremen (Germany)

Published in SPIE Proceedings Vol. 4465:
Organic Photovoltaics II
Zakya H. Kafafi; Denis Fichou, Editor(s)

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