Dye-Sensitized Oxide Semiconductors

On the other hand, oxide semiconductor materials such as ZnO and 2 have good stabilities under irradiation in solution. However, such stable oxide semiconductors cannot absorb visible light because of their wide band-gap character. Sensitization of wide-band-gap oxide semiconductor materials by photosensitizers, such as organic dyes which can absorb visible light, has been extensively studied in relation to the development of photography technology since the middle of the nineteenth century. In the sensitization process, dyes adsorbed onto the semiconductor surface absorb visible light and excited electrons of dyes are injected into the conduction band of the semiconductor. Dye-sensitized oxide semiconductor photoelectrodes have been used for PECs. 

Youngblood JW, Lee SHA, Maeda K, Mallouk TE (2009) Visible light water splitting using dye-sensitized oxide semiconductors. Acc Chem Res 42 1966-1973... 

Visible Light Water Splitting Using Dye-Sensitized Oxide Semiconductors."... 

The observation of photocurrent from dye sensitized planar semiconductors led to the evolution of the DSSC, on the basis of extremely high surface area nanoparticulate oxides, usually Ti02. The most successful dye for sensitization, N3, ds-bis(isothiocyanato) bis(2,2 -bipyridyl-4,4 dicarboxylato) ruthenium (II), employs several carboxylic acid groups for adsorption to Ti02, ZnO, Sn02, and/or ITO from an ethanol or acetonitrile solution over a several-hour period [32]. Electron injection from the excited state of this dye to the conduction band... 

In summary, at nanostructured tin-oxide semiconductor-aqueous solution interfaces, back ET to molecular dyes is well described by conventional Marcus-type electron-transfer theory. The mechanistic details of the reaction, however, are remarkably sensitive to the nature of the semiconductor-dye binding interactions. The mechanistic differences point, potentially, to differing design strategies for kinetic optimization of the corresponding liquid-junction solar cells. 

Ruthenium bipyridyl complexes are suitable photosensitizers because then-excited states have a long lifetime and the oxidized Ru(III) center has a longterm chemical stability. Therefore, Ru bipyridyl complexes have been studied intensively as photosensitizers for homogeneous photocatalytic reactions and dye-sensitization systems. The Ru bipyridyl complex, bis(2,2 -bipyridine)(2,2 -bipyri-dine-4, 4,-dicarboxylate)ruthenium(II), having carboxyl groups as anchors to the semiconductor surface was synthesized and single-crystal Ti02 photoelectrodes sensitized by this Ru complex were studied in 1979 and 1980 [5,6]. 

Dye-Sensitized Solar Cells Based on Mesosoopic Oxide Semiconductor Films... 

There has been a growing interest in inorganic/organic hybrid materials in recent years with expectations for new or improved properties, which are not exhibited or attainable by using the parent materials separately. The usefulness of such materials has been best manifested by recent successful studies of dye-sensitized solar cells, which typically employ thin film electrodes of porous oxide semiconductors such as TiOz, and whose surface is modified with sensitizing... 

There are, however, several fields of current research in which a corresponding level of understanding would be of interest also for large molecular adsorbates. For example, adsorbate-substrate interactions are relevant in the general areas of biocompatibility [51] and chemical sensors [52]. The requirement of dye-sensitization of metal oxide semiconductors also makes this an important aspect of many molecular photovoltaic devices. In fact, a good interfacial contact between dye and substrate, characterized by long-term stability and intimate electric contact, is vital for the efficiency of e.g. the dye-sensitized solar cells which have been at the center of our attention for the last five years. 

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