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摘要
Benzimidazole-branched bi-anchoring organic dyes that contained triphenylamine/phenothiazine donors, 2-cyanoacrylic acid acceptors, and various pi linkers were synthesized and examined as sensitizers for dye-sensitized solar cells. The structure-activity relationships in these dyes were systematically investigated by using absorption spectroscopy, cyclic voltammetry, and density functional theory calculations. The wavelength of the absorption peak was more-heavily influenced by the nature of the pi linker than by the nature of the donor. For a given donor, the absorption maximum (lambda(max)) was red-shifted on changing the pi linker from phenyl to 2,2'-bithiophene, whilst the dyes that contained triphenylamine units displayed higher molar extinction coefficients (epsilon) than their analogous phenothiazinebased triphenylamine dyes, which led to good light-harvesting properties in the triphenylamine-based dyes. Electrochemical data for the dyes indicated that the triphenylamine- based dyes possessed relatively low-lying HOMOs, which could be beneficial for suppressing back electron transfer from the conduction band of TiO2 to the oxidized dyes, owing to facile regeneration of the oxidized dye by the electrolyte. The best performance in the DSSCs was observed for a dye that possessed a triphenylamine donor and 2,2'-bithiophene pi linkers. Electron impedance spectroscopy (EIS) studies revealed that the use of triphenylamine as the donor and phenyl or 2,2'-bithiophene as the pi linkers was beneficial for disrupting the dark current and charge-recombination kinetics, which led to a long electron lifetime of the injected electrons in the conduction band of TiO2.
- 出版日期2016-9
