Structural effect of donor in organic dye on recombination in dye-sensitized solar cells with cobalt complex electrolyte.

The effect of the donor in an organic dye on the electron lifetime of dye-sensitized solar cells (DSSCs) employing a cobalt redox electrolyte was investigated. We synthesized organic dyes with donor moieties of carbazole, coumarin, triphenylamine, and N-phenyl-carbazole and measured the current-voltage characteristics and electron lifetimes of the DSSCs with these dyes. The cell with the triphenylamine donor dye produced the highest open circuit voltage and longest electron lifetime. On the other hand, the lowest open circuit voltage and shortest electron lifetime was obtained with coumarin donor dye, suggesting that the coumarin attracted the cobalt redox couples to the surface of the TiO2 layer, thus increasing the concentration of cobalt complex. On the other hand, the longest electron lifetime with triphenylamine was attributed to the blocking effect by steric hindrance of the nonplanar structure of the donor.