Functional supramolecular ruthenium cyclodextrin dyes for nanocrystalline solar cells

A suprarnolecular complex [Ru(dcb)₂(a-CD-5-bPY)]Cl₂ (1-α-CD) (dcb=4,4'-dicarboxyl-2,2'-bipyfidine, α-CD-5-bpy= 6-mono[5-methyl(5'-methyl-2,2'-bipyridyl)]-permethylated α-CD) (CD: cyclodextrin) based on a ruthenium tris-bipyridyl core with an appended α-CD cavity is designed and synthesisled, in order to facilitate dye/redox couple interaction and dye regeneration in nanocrystalline TiO₂ solar cells. The luminescent complex is fully characterized and anchored on mesoporous titania electrodes showing increased power-conversion efficiency in solid-state dye-sensitized solar cells using a composite polymer electrolyte. Direct comparison of the properties of the CD complex with an analogous ruthenium complex [Ru(dcb)₂(5,5'-dmbpy)] Cl₂ (2) (5,5'-dmbpy = 5,5'-dimethylbipyridin) without the CD cavity reveals that the photovoltaic performance of 1-α- CD is enhanced by about 40 % compared, to 2. Independent studies have shown complexation of the iodide redox couple to the CD in 1-α-CD. These results indicate that the CD moiety is able to act as a mediator and fine tune the photoelectrolyte interface.