Structural Characterization of Solar Cell Prototypes Based on Nanocrystalline TiO₂ Anatase Sensitized with Ru Complexes. X-ray Diffraction, XPS, and XAFS Spectroscopy Study

Prototype solar cells made up of nanocrystalline anatase supported on a conducting glass and sensitized with two Ru 2+ complexes ( cis -dithiocyanatobis(2,2‘-bipyridine-4,4‘-dicarboxylate)ruthenium(II), or red dye, and (4,4‘,4‘ ‘-tricarboxy-2,2‘:6‘,2‘ ‘-terpyridine)ruthenium(II), or black dye) are characterized with out-of-plane X-ray diffraction, X-ray photoelectron spectroscopy, and Ti K-edge XAFS (XANES and EXAFS), as well as by powder X-ray diffraction of the pure dyes used for a coating of a TiO 2 layer. The data indicate, within the sensitivity limits of the methods applied, that the dyes most probably form (partial coverage) a monolayer at the surface of anatase nanoparticles. Coating with the dyes leads to a stronger distortion of the local environment of Ti atoms in anatase nanoparticles.