Within today’s global challenge to capture and utilize solar energy for a sustainable development on a grand scale, dye sensitized solar cells (DSC), represent a particularly promising approach to the direct conversion of light into electrical energy at low cost and with high efficiency. In these devices, a dye sensitizer absorbs the solar radiation and transfers the photoexcited electron to a wide band-gap semiconductor electrode consisting of a mesoporous oxide layer composed of nanometer-sized particles, while the concomitant hole is transferred to the redox electrolyte or to a hole conductor. Ruthenium(II) complexes are widely employed as dye sensitizers, delivering record efficiencies in DSC. For further progress, however, higher conversion efficiencies need to be achieved. New sensitizers with tailored optical properties and a deeper understanding of the interaction between the dye and the TiO2 nanostructured electrode are essential.