Preparation, Characterization and Optical properties of a Dendritic Dye Sensitizer DDS-TiO2 hybrid material

We report a new triphenylamine-based dye having a dendritic structure (DDS) with one OH-ending able to interact with the surface hydroxyl moieties of a porous TiO2.We present the optical properties of the dye-titania composite showing that the dye performs more efficiently on a pure anatase TiO2 than on the commercial Degussa P25. The synthesized organic molecule and the hybrid material obtained by impregnation of DDS on the TiO2 porous structures were characterized by different techniques including 1H NMR, XPS, XRD, SEM and TEM. XRD confirms that the synthesized TiO2[1] is composed of pure anatase phase, whereas the commercial Degussa P25 contains a 20% of rutile phase. SEM and TEM show that the building blocks of the porous structure are nanoparticles of 20-30 nm in size. Physisorption measurements indicate that both the porous structure are quite disordered, and that the specific surface areas are similar. Optical measurements (Figure) show that the absorption of the dye in the pure anatase sample is more efficient than that in P25. The presence of DDS in pure anatase extends the spectral region resulting for example potentially useful for conversion of photons into electrical current in a DSSC [2] making it a promising candidate as a metal-free dye for DSSCs