Ruthenium sensitizers based on heteroaromatic conjugated bipyridines for dye-sensitized solar cells

A new ruthenium sensitizer based on a heteroaromatic-4,4'-pi-conjugated 2,2'-bipyridine, bearing conjugated pi-excessive heteroaromatic rings as donors is presented. Dye-sensitized solar cells have been fabricated based on the novel ruthenium complex [Ru(II)LL'(NCS)(2)] (L = 4,4'-bis[(E)-2-(3,4-ethylenedioxythien-2-yl)vinyl]-2,2'-bipyridine, L' = 4,4'-(dicarboxylic acid)-2,2'-bipyridine) and their photoelectrochemical properties have been measured under various conditions. Using this sensitizer photovoltaic efficiencies up to 9.1% under standard global AM 1.5 sunlight were obtained. DFT/TDDFT calculations have been performed for the sensitizer in solution. By calculating the excited states energy and character and comparing the results with the conduction band edge of a model TiO2 nanoparticle, we were able to highlight the factors affecting the measured photovoltaic efficiencies.