Infoscience

Journal article

Linker unit modification of triphenylamine-based organic dyes for efficient cobalt mediated dye-sensitized solar cells

Linker unit modification of donor-linker-acceptor-based org. dyes was investigated with respect to the spectral and physicochem. properties of the dyes. The spectral response for a series of triphenylamine (TPA)-based org. dyes, called LEG1-4, was shifted into the red wavelength region, and the extinction coeff. of the dyes was increased by introducing different substituted dithiophene units on the π-conjugated linker. The photovoltaic performance of dye-sensitized solar cells (DSCs) incorporating the different dyes in combination with cobalt-based electrolytes was found to be dependent on dye binding. The binding morphol. of the dyes on the TiO2 was studied using photoelectron spectroscopy, which demonstrated that the introduction of alkyl chains and different substituents on the dithiophene linker unit resulted in a larger tilt angle of the dyes with respect to the normal of the TiO2-surface, and thereby a lower surface coverage. The good photovoltaic performance for cobalt electrolyte-based DSCs found here and by other groups using TPA-based org. dyes with a cyclopentadithiophene linker unit substituted with alkyl chains was mainly attributed to the extended spectral response of the dye, whereas the larger tilt angle of the dye with respect to the TiO2-surface resulted in less efficient packing of the dye mols. and enhanced recombination between electrons in TiO2 and Co-(III) species in the electrolyte.

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