The electrochemical and photoelectrochemical study of noncorrosive electron-transfer mediator mixtures for DSC is reported. These mixtures, characterized by the presence of kinetically fast organic or metal-organic redox couples in conjunction with a Co(II)/(III) relay, exhibited maximum photon-to-current conversion efficiencies (IPCE %) exceeding 80% when employed in the presence of a suitably designed MLCT sensitizer, rivaling with the performances of the classical I-/I3- electrolyte.

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Dye-sensitized solar cells (DSSCs) were assembled by using the bougainvillea flowers, red turnip and the purple wild Sicilian prickly pear fruit juice extracts as natural sensitizers of TiO2 films. The yellow orange indicaxanthin and the red purple betacyanins are the main components in the cocktail of natural dyes obtained from these natural products. The best overall solar energy conversion efficiency of 1.7% was obtained, under AM 1.5 irradiation, with the red turnip extract, that showed a remarkable current density (Jsc = 9.5 mA/cm2) and a high IPCE value (65% at λ = 470 nm). Also the purple extract of the wild Sicilian prickly pear fruit showed interesting performances, with a Jsc of 9.4 mA/cm2, corresponding to a solar to electrical power conversion of 1.26%.

The effect of pyrrole- and pyrrolidine-containing ligands (L) on the properties of heteroleptic [RuL2dcbpy]2+ complexes has been investigated. TiO2 electrodes modified with the new complexes exhibited extended absorption domains and high absorbances. Providing that a cobalt-based mediator was used for regeneration of the RuII state, good incident photon-to-current efficiency (near 80%) values were obtained in the pyrrole series.

A new Ru(L)(dcbpy)(NCS)2 dye containing a pyrrole-based pi-extended ligand has been prepared and showed very good light harvesting ability with near 70% IPCE in the visible region. The performance is very close to those of the standard N3 with a wider absorption range.