Engineering of Ruthenium(II) Photosensitizers with Non‐Innocent Oxyquinolate and Carboxyamidoquinolate Ligands for Dye‐Sensitized Solar Cells

An alternative approach to replacing the isothiocyantate ligands of the N3 photosensitizer with light‐harvesting bidentate ligands is investigated for application in dye‐sensitized solar cells (DSSCs). An in‐depth theoretical analysis has been applied to investigate the optical and redox properties of four non‐innocent ligand platforms, which is then corroborated with experiment. Taking advantage of the 5‐ and 7‐positions of 8‐oxyquinolate, or the carboxyaryl ring system of the N‐arylcarboxy‐8‐amidoquinolate ligand, fluorinated aryl substituents are demonstrated as an effective means of tuning complex redox potentials and light‐harvesting properties. The non‐innocent character, resulting from mixing of both the central metal‐dπ and ligand‐π manifolds, generates hybrid metal–ligand frontier orbitals. These play a major role by contributing to the redox properties and visible electronic transitions, and promoting an improved power conversion efficiency in a Ru DSSC device featuring non‐innocent ligands. Oxyquinolate and carboxyamidoquinolate ligands were investigated experimentally and theoretically for their influence on the optical and redox properties of ruthenium dyes for application in dye‐sensitized solar cells. Fluorination of these non‐innocent ligands has a positive influence on the frontier orbital mixing with the central ruthenium metal, thereby contributing to (metal‐ligand)‐to‐ligand charge‐transfer electronic transitions (see figure).