title: Impact of the molecular structure and adsorption mode of D-π-A dye sensitizers with a pyridyl group in dye-sensitized solar cells on the adsorption equilibrium constant for dye-adsorption on TiO2surface.
abstract: D-π-A dyes NI-4 bearing a pyridyl group, YNI-1 bearing two pyridyl groups and YNI-2 bearing two thienylpyridyl groups as the anchoring group on the TiO2surface have been developed as dye sensitizers for dye-sensitized solar cells (DSSCs), where NI-4 and YNI-2 can adsorb onto the TiO2electrode through the formation of the coordinate bond between the pyridyl group of the dye and the Lewis acid site (exposed Tin+cations) on the TiO2surface, but YNI-1 is predominantly adsorbed on the TiO2electrode through the formation of the hydrogen bond between the pyridyl group of the dye and the Brønsted acid sites (surface-bound hydroxyl groups, Ti-OH) on the TiO2surface. The difference in the dye-adsorption mode among the three dyes on the TiO2surface has been investigated from the adsorption equilibrium constant (Kad) based on the Langmuir adsorption isotherms. It was found that the Kadvalues of YNI-1 and YNI-2 are higher than that of NI-4, and more interestingly, the Kadvalue of YNI-2 is higher than that of YNI-1. This work demonstrates that that for the D-π-A dye sensitizers with the pyridyl group as the anchoring group to the TiO2surface the number of pyridyl groups and the dye-adsorption mode on the TiO2electrode as well as the molecular structure of the dye sensitizer affect the Kadvalue for the adsorption of the dye to the TiO2electrode, that is, resulting in a difference in the Kadvalue among the D-π-A dye sensitizers NI-4, YNI-1 and YNI-2.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan. yooyama@hiroshima-u.ac.jp.
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Ooyama
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan. yooyama@hiroshima-u.ac.jp.
authors.forename: Naoya
authors.initials: N
authors.lastname: Yamaguchi
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan. yooyama@hiroshima-u.ac.jp.
authors.forename: Joji
authors.initials: J
authors.lastname: Ohshita
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan. yooyama@hiroshima-u.ac.jp.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Harima