Influence of Lithium Ions on the Ion-coordinating Ruthenium Sensitizers for Nanocrystalline Dye-sensitized Solar Cells

Ion-coordinating ruthenium complexes [cis-Ru(dcbpy)(L)(NCS)(2), where dcbpy is 4,4'-dicarboxylic acid-2,2'-bipyridine and L is 1,4,7,10-tetraoxa-13-azacyclopentadecane, JK-121, or bis(2-(2-methoxy-ethoxy)ethyl) amine, JK-122] have been synthesized and characterized using H-1 NMR, Fourier transform IR, UV/vis spectroscopy, and cyclic voltammetry. The effect of Li+ in the electrolyte on the photovoltaic performance was investigated. With the stepwise addition of Li+ to a liquid electrolyte, the device shows significant increase in the photo-current density, but a small decrease in the open circuit voltage. The solar cell with a hole conductor, the addition of Li+ resulted in a 30% improvement in efficiency. The JK-121 sensitized cells in the liquid and solid-state electrolyte give power conversion efficiencies of 6.95% and 2.59%, respectively, under the simulated sunlight.