Influence of Dye Architecture of Triphenylamine Based Organic Dyes on the Kinetics in Dye-Sensitized Solar Cells

The impact of the dye architecture on the kinetics in the dyesensitized solar cell (DSC) was investigated for two structurally similar organic dyes, adsorbed adsorbed to a mesoporous TiO2 film. Differences in the HOMO and LUMO levels of the triphenylamine dyes D35 and D45 were negligible, indicating that the changes in kinetics of the electron transfer processes in the solar cells can be attributed to structural differences of the organic dyes. The electron transfer kinetics of various processes was investigated by scanning electrochemical microscopy (SECM), transient absorption spectroscopy (TAS), and impedance spectroscopy (IS). SECM was used for the first time to determine the rate constants of the regeneration (reduction) of a photooiddized organic dye by a oneelectron cobalt mediator. Both TAS and IS measurements showed differences in recombination of electrons in TiO2, with oxidized D35 and D45. D45 with its shorter dimethoxyphenyl units yielded faster recombination and regeneration than D35, as measured by SECM and TAS. The results of this study show that small details in the dye structure significantly affect the kinetics of organic triphenylamine dye based dye-sensitized solar cells.