Amphiphilic ruthenium sensitizer with 4,4′-diphosphonic acid-2,2′-bipyridine as anchoring ligand for nanocrystalline dye sensitized solar cells

A new amphiphilic polypyridyl ruthenium complex, cis-Ru(dpbpy)(dnbpy)(NCS)2 (dpbpy = 4,4'-diphosphonic acid-2,2'-bipyridine; dnbpy = 4,4'-dinonyl-2,2'-bipyridine), was synthesized and demonstrated as an efficient sensitizer. The sensitizer was characterized by NMR, voltammetry, ATR-FTIR, resonance Raman, as well as electronic absorption and emission spectra. Nanocrystalline dye-sensitized solar cells (DSCs) with this new sensitizer generated greater than or equal to8.0% power conversion efficiencies under illumination with simulated air mass 1.5 sunlight. This is the first time such a high solar-to-electricity power conversion efficiency for DSCs has been reached by a sensitizer hearing non-carboxylic acid anchoring groups. Additionally, the devices exhibited excellent stability under light soaking at 55 to 60degreesC. Time-resolved nanosecond laser experiments revealed that the dye regeneration rate of this new sensitizer seems to be quite similar but the charge recombination is significantly slower in comparison to the analogues carboxylated sensitizer.