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

The D-pi-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 pi-bridge and hexyloxy side chains in donor moieties on carrier injection efficiencies, electron diffusion length and dye-regeneration efficiencies. Retarded charge recombination of e(TiO2)-/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-pi-A dyes. (c) 2013 Elsevier B.V. All rights reserved.