New Efficient Ruthenium Sensitizers with Unsymmetrical Indeno[1,2<i>-b</i>]thiophene or a Fused Dithiophene Ligand for Dye-Sensitized Solar Cells

Two novel ruthenium sensitizers containing unsymmetrical indeno[1,2<i>-b</i>]thiophene or a fused dithiophene unit in the ancillary ligand have been designed and synthesized. The photovoltaic performance of <b>JK-188</b> using an electrolyte consisting of 0.6 M 1,2-dimethyl-3-propylimidazolium iodide, 0.05 M I<sub>2</sub>, 0.1 M LiI, 0.05 M guanidinium thiocyanate, and 0.5 M <i>tert</i>-butylpyridine in acetonitrile revealed a short-circuit photocurrent density of 18.60 mA/cm<sup>2</sup>, an open-circuit voltage of 0.72 V, and a fill factor of 0.71, yielding an overall conversion efficiency of 9.54%. The cell exhibits a remarkable stability under 1000 h of light soaking at 60 °C using a quasi-solid-state electrolyte consisting of 5 wt % poly(vinylidenefluoride-<i>co</i>-hexafluoropropylene), 0.6 M 1-propyl-2,3-dimethylimidazolium iodide, 0.5 M <i>N</i>-methylbenzimidazole, and 0.1 M I<sub>2</sub> in 3-methoxypropionitrile, retaining 97% of the initial efficiency (7.38%).