Light-harvesting in the near-infrared region: Dye-sensitized solar cells sensitized with asymmetric ring-expanded zinc(II) phthalocyanines

Abstract

A near-IR absorbing dye (FcS1), in which three fluorene rings were fused with a porphyrazine ring, has been designed and synthesized as a photosensitizer for dye-sensitized solar cells (DSSCs). The fusion of the fluorene rings led to tailoring of the HOMO and LUMO energy levels as well as an expansion of the p-system. The absorption spectrum of FcS1 adsorbed onto a nanocrystalline TiO2 film suggested the formation of J-aggregates with tilted orientation of the macrocyclic ligands. While the power conversion efficiency of DSSCs sensitized with FcS1 was a modest 3.2% under simulated air mass 1.5 global sunlight, FcS1 can convert the red and near-IR light regions between 600 and 860nm into electricity.