ZnO has been cathodically electrodeposited from oxygen-saturated ZnCl2 solution in the presence of monosaccharides as
additives. While glucose had no influence on the morphology of the deposited ZnO films, a significant influence could
be seen in the presence of glucuronic acid, showing that acidic groups are essential to obtain an influence on the film
growth by enabling a strong interaction between the additive and the surface of the growing ZnO. The resulting films had
a porous structure probably caused by the integration of aggregated additives as confirmed by TEM measurements. In
addition, the films were found to have a strong crystallographic orientation as seen in the formation of stacking disc-like
particles in SEM micrographs and confirmed by a strong 100 orientation observed in XRD measurements. A comparison
with earlier results obtained with phthalocyanine dyes as additives in the electrodeposition of ZnO shows that additional
OH groups in the additive molecules play an important role for the formation of this crystallographic orientation.
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.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.