Simple NIR Complexes and Their Applicability in Dye-Sensitized Solar Cells

Novel nickel(II)benzo-diimino-semiquinonate and palladium(II)benzo-imino-semiquinonate complexes were synthesized, tested regarding their applicability in dye sensitized solar cells, and characterized optically and electrochemically. All the dyes showed a strong absorption in the near infrared region. Various electron-withdrawing substituents were introduced into the complex ligands and evaluated with respect to the effect on the energy level of the frontier molecular orbitals. Energetically suitable complexes were then tested in TiO2 based dye-sensitized solar cells with different iodide-based electrolytes. Two of them exhibited energy conversion abilities suggesting their candidacy as co-sensitizers to known visible light-absorbing dyes in order to extend the spectral window used for light harvesting into the infrared region to increase the total conversion efficiency of the cell.