Terpyridyl Ruthenium Complexes Functionalized with Conjugated Heterocycles for Panchromatic Dye-Sensitized Solar Cells

Photosensitizer, a key component of dye-sensitized solar cells (DSCs), significantly affects the power conversion efficiency (PCE) of the devices. In this study, three terpyridyl (tpy) ruthenium complex dyes incorporating hexyl-substituted pyrrole (CYC-36), 4-methylthiazole (CYC-39), and thieno[3,2-b]pyrrole (CYC-41) were designed and their photovoltaic performance was examined. To the best of our knowledge, this study introduced these heterocyclic conjugated rings to functionalize the tpy-coordinated ruthenium complexes and discovered that 4-methylthiazole in the anchoring ligand of CYC-39 simultaneously enhanced the lighting-harvesting capability of the dye molecule, increased dye-loading in TiO2 photoanode, and reduced the charge recombination in the cells. The multifunction of 4-methylthiazole moiety is ascribed to not only the aromaticity and electron-withdrawing nature but also the formation of a moderate dihedral angle between the thiazole ring and the tpy core. Consequently, the DSC device sensitized with CYC-39 yields not only a panchromatic response up to 900 nm but also a good PCE of 9.0%.