I?3/I? Redox Behavior of Alkali-metal Iodide Complexes with Crown Ether/Cryptand Macrocycles and Their Applications to Dye-sensitized Solar Cells

In this article, the I−3/I− redox behavior in 3-methoxypropionitrile (MePN) containing alkali-metal iodide com-plexes with crown ether and cryptand macrocycles was studied by cyclic voltammetry. It was found that the apparent diffusion coefficient D values of triiodide and iodide ions correlate with cations. D values of triiodide follow the order: 1,2-dimethyl-3-propylimidazolium cation (DMPI+)>[Na⊂15-C-5]+ (the mathematical symbol of inclusion, ⊂, was used to indicate Na+ included in 15-C-5)>[K⊂18-C-6]+>[Na⊂2.2.1-cryptand]+ and those of iodide ions follow the order: [Na⊂2.2.1-cryptand]+>[Na⊂15-C-5]+ ≈[K⊂18-C-6]+ >DMPI+. The photovoltaic performances of dye-sensitized solar cells (DSC) with these complexes were compared with those containing 1,2-dimethyl-3-propylimidazolium iodide (DMPII) in MePN. It shows that DSC with these complexes gave a little higher short photocurrent intensity and lower fill factor than those with DMPII, which is consistent with D values of triiodide and iodide ions. Moreover, solvents played an important role for the photo-electric conversion efficiency of DSC. The photo-electric conversion efficiency of DSC with DMPII is higher than that with [K⊂18-C-6]I in MePN, while in ACN, it shows a little difference.