Molecular design rule of phthalocyanine dyes for highly efficient near-IR performance in dye-sensitized solar cells.

A series of zinc-phthalocyanine sensitizers (PcS16-18) with different adsorption sites have been designed and synthesized in order to investigate the dependence of adsorption-site structures on the solar-cell performances in zinc-phthalocyanine based dye-sensitized solar cells. The change of adsorption site affected the electron injection efficiency from the photoexcited dye into the nanocrystalline TiO2 semiconductor, as monitored by picosecond time-resolved fluorescence spectroscopy. The zinc-phthalocyanine sensitizer PcS18, possessing one carboxylic acid directly attached to the ZnPc ring and six 2,6-diisopropylphenoxy units, showed a record power conversion efficiency value of 5.9 % when used as a light-harvesting dye on a TiO2 electrode under one simulated solar condition.