A Dendritic Oligothiophene Ruthenium Sensitizer for Stable Dye-Sensitized Solar Cells

We report a new type of dendritic terthiophene attached to a 2,2'-bipyridine ligand for ruthenium-based dye-sensitized solar cells. As a result of the incorporation of this electron-rich terthiophene donor unit into the heteroleptic ruthenium sensitizer [Ru(dcbpy)(3Tbpy)(NCS)(2)] (3T), the lowest-energy metal-to-ligand charge transfer (MLCT) transition is red-shifted and the molar extinction coefficient is increased compared to the analogous standard Z907Na sensitizer. A preliminary investigation of the 3T dye in combination with an iodine/iodide-based electrolyte shows an interesting photovoltaic performance, with a maximum power conversion efficiency of 7.4% measured under air mass 1.5 global sunlight irradiation. Accelerated testing of these devices at 60 degrees C under full sunlight soaking shows a remarkable stability over 1000 h.