Contributions to the development of ruthenium-based sensitizers for dye-sensitized solar cells

The present review article traces the discoveries that were instrumental to the evolution of DSSCs, taking a critical look at the principles of the operation mechanism and insisting on the most important recent developments in the field. We draw our attention mainly to the dye (photosensitizer); the primary processes that take place inside a solar cell, and which are affected by the dye, are also reviewed along with some of the most significant recent information found in literature that one should keep in mind before designing a novel ruthenium sensitizer. Specific emphasis is given in trying to answer vital questions like defining the optimum number of -COOH anchoring groups and protons that an efficient dye should carry, the correct choice of preparing either a homoleptic or a heteroleptic complex, as well as which counterions are the most suitable. Phenomena such as the role of the adsorption geometry, electrical fields at the double layer, dye-redox couple interaction and recombination effects are also analyzed, in order to show how these factors influence the photoelectrochemical characteristics of the cell. Next, the contributions from our group in the direction of designing, synthesizing, characterizing and evaluating novel ruthenium(II)-based complexes, utilized as photosensitizers in DSSCs, are thoroughly discussed. Two types of Ru(II) complexes are examined: one family mimicking the standard N719 dye, bearing bidentate ligands, and another, carrying tridendate ligands, resembling the black dye. (C) 2010 Elsevier B.V. All rights reserved.