Functional Supramolecular Ruthenium Cyclodextrin Dyes for Nanocrystalline Solar Cells

A supramolecular complex [Ru(dcb) 2 (α‐CD‐5‐bpy)]Cl 2 ( 1‐α‐CD ) (dcb = 4,4′‐dicarboxyl‐2,2′‐bipyridine, 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 synthesised, in order to facilitate dye/redox couple interaction and dye regeneration in nanocrystalline TiO 2 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)]Cl 2 ( 2 ) (5,5′‐dmbpy = 5,5′‐dimethylbipyridine) 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 photoelectrode/electrolyte interface.