Complementary co-sensitization of an aggregating squaraine dye in solid-state dye-sensitized solar cells

In this study, we used the co-sensitization approach to reach panchromatic light absorption in solid-state dye-sensitized solar cells (SDSCs). We combined two complementary absorbing organic sensitizers, viz, a blue-absorbing triphenyldiamine dye (TPD-dye) and a red-absorbing squaraine dye (SQ-dye). The aggregation behaviour of SQ-dye was entirely investigated by steady-state UV/vis spectroscopy. The formation of H- and J-aggregates was observed in both solution and the chemisorbed state on mesoporous TiO2. On applying SQ-dye and TPD-dye in single-dye and co-sensitized SDSCs, the external quantum efficiency studies clearly indicate that TPD-dye, as well as the monomer species and the H- and J- aggregates of SQ-dye contribute to the current generation. We optimized the performance of the co-sensitized SDSCs regarding the solvent used for the chemisorption, the chemisorption time, and the thickness of the mesoporous TiO2 layer. The best result was obtained for a co-sensitized SDSC after chemisorption for 3 h from a tert-butanol/acetonitrile 1:1 solution using a 1.4 mu m thick mesoporous TiO2 layer. (C) 2013 Elsevier Ltd. All rights reserved.