New class of thiocyanate-free cyclometalated ruthenium(II) complexes having a pyridylquinoline derivative for near-infrared sensitization of dye-sensitized solar cells

A new class of thiocyanate-free cyclometalated ruthenium(II) complexes [Ru(dcpq)2(C^N)]Cl (where dcpq is 4-carboxy-2-(4′-carboxypyridin-2′-yl)quinoline and C^N is a bidentate cyclometalating ligand) (FT22 and FT61) was synthesized as near-infrared (IR) sensitizers for dye-sensitized solar cells (DSSCs). Modification of the ligand improves photovoltaic performance, and DSSCs sensitized with FT61 show large photocurrents (> 21 mA cm− 2) as well as a 55% incident photon-to-current conversion efficiency (IPCE) at 800 nm and 25% IPCE at 900 nm. The complexes exhibit superior light-harvesting properties in the near-IR region.