Homoleptic Ruthenium Complex Bearing Dissymmetrical 4-Carboxy-4′-pyrrolo-2,2′-bipyridine for Efficient Sensitization of TiO2 in Solar Cells

An easily accessible homoleptic complex [Ru(L3)(3)](2+) containing a dissymmetrical bipyridine (L3) substituted by a pyrrole and a carboxylic group has been evaluated in a dye-sensitized solar cell. The new dye displayed extended absorption domain, high absorbance, and a promising 65% IPCE value. Higher scores were reached using a cobalt-iron mediator instead of the usual LiI/I(2) couple for regeneration of the Ru(II) state. Transient absorption spectroscopy was used to explain the mediator effect.