A highly efficient redox chromophore for simultaneous application in a photoelectrochemical dye sensitized solar cell and electrochromic devices

Abstract

We synthesized a novel series of compounds based on a ruthenium(II) dicarboxybipyridine (dcbpy) complex containing chloro and trans-1,4-bis[2-(4-pyridyl)ethenyl]benzene (BPEB) ligands. The binuclear species Na₆[{[Ru^II(dcbpy)₂Cl}₂(BPEB)] exhibits an electrochromic effect when reduced, which is assigned to the radical BPEB^0/˙, similarly as in viologen-based compounds. The carboxylate groups on the 4,4′ positions of bipyridine allow a strong attachment to the TiO₂ surface, contributing to an efficient and reversible electron transfer from the oxide to the chromophoric ligand, coloring the oxide film blue. The coloration efficiency CE(λ) at 633 nm was 109 cm² C⁻¹, which is high compared to TiO₂ itself. The complex also exhibits a high photon-to-electron conversion efficiency (IPCE > 70%) when applied as a photoanode in a dye sensitized solar cell (DSSC).