Photophysical studies on D–π–A dye-sensitized solar cells: Effects of π-bridge and hexyloxy side chains in donor moieties

The D–π–A organic dyes which feature diphenylthienylamines as the donors and cyanoacrylic acid as the acceptors, are carefully examined. Comprehensive spectral response analysis and transient techniques are exploited to investigate the effects of various functionalized π-bridge and hexyloxy side chains in donor moieties on carrier injection efficiencies, electron diffusion length and dye-regeneration efficiencies. Retarded charge recombination of eTiO2-/electrolytes+ is found in molecules with the hexyloxy chains and diphenyl-substituted dithienosilole groups. However, regeneration rate is revealed as being slower with the larger sensitizer structure and the higher HOMO levels. A clear trade-off between charge recombination and dye regeneration is found and should be taken into account in future molecular designs of D–π–A dyes.

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► The D–π–A dyes with various π-bridge and side chains were carefully examined.
► Comprehensive analyses are exploited to investigate the carrier dynamics.
► Retarded recombination is found in dyes with the hexyloxy chains and DTS groups.
► Regeneration rate is slower with the larger sensitizer structure.
► A clear trade-off between charge recombination and dye regeneration is found.