Ruthenium complex dye with designed ligand capable of chelating triiodide anion for dye-sensitized solar cells

Ru(4,4′-dicarboxyl-2,2′-bipyridine)[4,4′- bis(styrylaminocarbonyl)-2,2′-bipyridine](NCS)2, denoted as RuAS dye, was synthesized and well characterized by 1H-NMR, 13C-NMR, heteronuclear single quantum coherence, UV-vis and ESI-MS spectra. Its capability of chelating triiodide anions with the 4,4′-bis(styrylaminocarbonyl)-2,2′-bipyridine ligand, which was revealed by ATR-FTIR and 1H-NMR spectroscopies, reduced the charge recombination for dye-sensitized solar cells (DSSCs) by keeping the triiodide ions away from contact with the mesoporous TiO2 layer. Therefore, the open-circuit photovoltage of the DSSC barely changed with the triiodide concentration in the electrolyte. Moreover, the electron-withdrawing ability of the amide groups in the ligand increased the molar extinction coefficient of the dye, leading to the increase of photocurrent for DSSCs. The enhanced photovoltaic performance was further examined by incident photon-to-current conversion efficiency spectra, electrochemical impedance spectroscopy and open-circuit potential decay transient measurements. © 2013 The Royal Society of Chemistry.