Dye sensitization of nanocrystalline TiO2: enhanced efficiency of unsymmetrical versus symmetrical squaraine dyes

A series of novel symmetrical and unsymmetrical squaraine dyes have been synthesized and their comparative efficiencies as photosensitizers in dye sensitized solar cells (DSSCs) containing nanocrystalline TiO2 photoelectrodes have been investigated. DSSCs employing unsymmetrical squaraines as sensitizers produced photocurrent with much higher efficiencies compared to DSSCs containing symmetrical squaraines. Aggregation of the dyes on the TiO2 nanocrystalline electrode was observed to adversely affect the sensitization properties of symmetrical squaraines, whereas efficient sensitization was observed from both the monomeric and aggregated forms of the unsymmetrical squaraines.