Coordinative interactions in a dye-sensitized solar cell

Resonance Raman scattering studies of a complete dye-sensitized solar cell (DSC) including iodine and lithium iodide in the electrolyte indicate that triiodide (I3−) exchange the SCN− ligand of the dye bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II). The choice of cation in the iodide salt influenced the ligand stability of the dye. It was proposed that an ion pair Li+⋯I3− formation occurred which by a reduced electrostatic repulsion between I3− and SCN− facilitated the exchange of these anions at Ru(II) of the dye. The additive 1-methylbenzimidazole (MBI) suppressed the SCN−/I3− ligand exchange by forming a complex with Li+. The concentrations of Li+ and MBI have to be carefully balanced due to the SCN− ligand exchange with MBI in deficiency of Li+. In order to observe and understand the prevailing coordinative interactions between the components in a DSC, the use of characterization methods with which complete devices can be studied is necessary.