A mass spectrometric analysis of sensitizer solution used for dye-sensitized solar cell

We report a mass spectrometric study of ruthenium(II) sensitizer ((C4H9)4N)2[Ru(4-carboxy-4′-carboxylate-2,2′bipyridine)2(NCS)2] (N719) in various organic and aqueous solvents. At the equilibrium different species were found, depending on solution properties. After stoichiometry confirmation through high-resolution mass spectra and isotopic pattern analysis, the formation of these complexes was found to strongly depend from the polarity and the ionic strength of solvent medium. Mass spectra obtained in acetonitrile/tert-butanol (1:1) mixture, used for the absorption of N719 on TiO2, suggests that the main species involved in the adsorption process is the dicarboxylate form of N719 with one (C4H9)4N as counter ion. The photovoltaic data of the N719 sensitizer adsorbed on TiO2 films exhibited a remarkable power conversion efficiency, 11.20% at 1 sun.