Tuning visible-light absorption properties of Ru-diacetylide complexes: simple access to colorful efficient dyes for DSSCs

A series of sigma-dialkynyl ruthenium complexes showing a D-pi-[M]-pi-A structure (where [M] - [Ru(dppe)(2)], dppe = bisdiphenylphosphinoethane) were designed and synthesized for dye-sensitized solar cell (DSSC) applications. The molecular structure of these highly modular organometallic complexes was fine-tuned through the introduction of a bithiophene, rhodanine or benzothiadiazole unit. This original molecular engineering approach combined with convergent synthetic pathways thus afforded efficient photosensitizers with tunable colors across the visible spectrum, ranging from red to purple, blue and blue-green dyes. The optoelectronic properties of the new complexes were fully assessed and the dyes were tested in standard single-dye devices as well as in co-sensitized DSSCs, yielding 7.5% power conversion efficiency in the presence of an iodine-based liquid electrolyte.