Resonance-Raman microspectroscopy for quality assurance of dye-sensitized NiO(x) films with respect to dye desorption kinetics in water.

Resonance Raman microspectroscopy is used to investigate dye-sensitized NiO(x) nanoparticle films to be used as photocathodes in tandem dye-sensitized solar cells. It is shown that rR microspectroscopy has potential for applications in quality assurance in such systems and also in integrated dye-sensitized solar cell modules. Here, ruthenium dye-sensitized NiO(x) nanoparticle layers were produced both as single and double NiO(x) films using a one or two-step deposition process, respectively. The distribution of the sensitizer on the surfaces was investigated by rR microspectroscopy. The chemical images obtained from rR microspectroscopy yield complementary information to bright field microscope pictures and provide detailed insight into the sensitization pattern e.g. in the vicinity of surface vacancies and other inhomogeneities. Furthermore, based on the mapping results the dye desorption kinetics upon addition of water has been analysed. Desorption on the single NiO(x) film is faster and more efficient than on the double film. These changes are attributed to binding sites on the NiO(x) surface that are passivated with regard to water penetration. This passivation is introduced by the second synthesis step in building the second film of NiO(x) on the glass substrate. Both findings highlight the potential of rR microspectroscopy for quality assurance of dye-sensitized solar cell electrodes.