Synthesis of ruthenium complex and its application in dye-sensitized solar cells

An amphiphilic bipyridyl ligand, 4,4′-dicarboxy-octyl-2,2′-bipyridine, and its ruthenium(□) complex (termed as S8) were synthesized and characterized by UV/Vis, IR and NMR spectroscopy. The performance of this S8 complex as charge transfer photo-sensitizer in TiO2-based dye-sensitized solar cells was studied under standard AM 1.5 sunlight and by using an electrolyte consisting of 0.70 M 1,2-dimethyl-3-propyl-imidazolium iodide, 0.10 M LiI, 40 mM iodine and 0.125 M 4-tert-butylpyridine in acetonitrile. Aliphatic chains linking to carboxylate groups of S8 act as an effective electron donor and carboxylate groups act as an effective electron withdrawing between the TiO2 layer and the carboxylate linking TiO2 layer leading to increasing of electron density at this interface, which is attributed to increasing efficiency of electron injection to the TiO2 conduction band from the excited state of dye. The complex, S8, gave a photocurrent density of 13.02 mA/cm2, 0.60 V open circuit voltage and 0.69 fill factor yielding 5.36% efficiency. The S8 dye with aliphatic chain improved conversion efficiency of the resulting DSSCs compared with a cell fabricated using the N3 dye.