Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

The use of conductivity measurements in organic solvents for the characterisation of coordination compounds

J. Appl. Cryst.の発刊に際して

A fundamental aim in the field of catalysis is the development of new modes of small molecule activation. One approach toward the catalytic activation of organic molecules that has received much attention recently is visible light photoredox catalysis. In a general sense, this approach relies on the ability of metal complexes and organic dyes to engage in single-electron-transfer (SET) processes with organic substrates upon photoexcitation with visible light.

Many of the most commonly employed visible light photocatalysts are polypyridyl complexes of ruthenium and iridium, and are typified by the complex tris(2,2′-bipyridine) ruthenium(II), or Ru(bpy)32+ (Figure 1). These complexes absorb light in the visible region of the electromagnetic spectrum to give stable, long-lived photoexcited states.1,2 The lifetime of the excited species is sufficiently long (1100 ns for Ru(bpy)32+) that it may engage in bimolecular electron-transfer reactions in competition with deactivation pathways.3 Although these species are poor single-electron oxidants and reductants in the ground state, excitation of an electron affords excited states that are very potent single-electron-transfer reagents. Importantly, the conversion of these bench stable, benign catalysts to redox-active species upon irradiation with simple household lightbulbs represents a remarkably chemoselective trigger to induce unique and valuable catalytic processes.






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Figure 1


Ruthenium polypyridyl complexes: versatile visible light photocatalysts.

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Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis

Excitonic solar cells1—including organic, hybrid organic–inorganic and dye-sensitized cells (DSCs)—are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient2 and stable3 excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.

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Nanowire dye-sensitized solar cells

Trends in metal-ligand orbital mixing in generic series of ruthenium n-donor ligand complexes : effect on electronic spectra and redox properties

Metal-free copper and cobalt(II) binuclear phthalocyanines, in which the two phthalocyanine nuclci are covalently linked through five-atom bridges, have been prepared and characterized. Some new metal-free, copper, cobalt(II), and zinc 2,9,16,23-tetraalkoxyphthalocyanines, some of which are extremely soluble in organic solvents, are described.

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Metallophthalocyanine dimers incorporating five-atom covalent bridges

: The electronic absorption and emission spectra of a series of mononuclear and binuclear metal-free phthalocyanine species are reported. The binuclear species are linked through a benzene ring by a bridge of 0,1,2,4 or 5 atoms. The spectroscopic data for the binuclear species, are analysed in terms of exciton coupling between the two halves of the molecule. Intramolecular coupling is seen to depend upon the nature of the bridging link. In some cases a cofacial conformation is possible; this gives rise to characteristic long-lived emission near 750 nm. Originator supplied keywords include: Electronic Coupling.

Intramolecular coupling in metal-free binuclear phthalocyanines

: The oxidation and reduction of metal phthalocyanines give rise to at least six oxidation states whose electronic spectra are rationalized in some depth in terms of SCF energies, Coulomb and exchange integrals. It is shown that a single set of parameters can reproduce the Q band energies moderately well. Further this same set of energies can reproduce differences in electrochemical potentials observed within this redox set. The pattern of variation in the Q band energies (and in their number) now provides a means for identifying whether it is the metal or the phthalocyanine ligand which is reduced upon addition of an electron to the system.

A. B. P. Lever

Papers

Trends in metal-ligand orbital mixing in generic series of ruthenium n-donor ligand complexes : effect on electronic spectra and redox properties

Metallophthalocyanine dimers incorporating five-atom covalent bridges

Intramolecular coupling in metal-free binuclear phthalocyanines

Electronic spectra of phthalocyanine radical anions and cations

Complexes of 2,2'-azopyridine with iron(II), cobalt(II), nickel(II), copper(I), and copper(II). Infrared study