Influence of quinoline derivatives in I−/I3− redox electrolyte solution on the performance of Ru(II)-dye-sensitized nanocrystalline TiO2 solar cell

The influence of quinoline additives in an I−/I3− redox electrolyte solution on the performance of a bis(tetra-butylammonium)cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) (N719) dye-sensitized TiO2 solar cell was studied. The I–V characteristics were measured for the cells with 20 types of quinoline derivatives. All of the quinoline additives enhanced the open-circuit photovoltage (Voc) and fill factor (ff), but reduced the short circuit photocurrent density (Jsc) of the solar cell. Most of the quinolines also improved the solar energy conversion efficiency (η). The physical and chemical properties of the quinolines were computationally calculated in order to elucidate the reasons for the additive effects on the cell performance. The greater the lowest partial charge of the atoms in the quinoline derivatives, namely nitrogen, the larger the Voc, but the smaller the Jsc values. As the dipole moment of the quinoline derivatives increased, the Voc value increased, but the Jsc value decreased. The Voc of the cell also increased as the ionization energy of the quinolines decreased. These results suggest that the electron donicity of the quinoline additives affected the interaction with the nanocrystalline TiO2 photoelectrode, the I−/I3− electrolyte, and the acetonitrile solvent, which changed the Ru(II)-dye-sensitized solar cell performance.