Design and synthesis of photosensitizers with alkoxysilane anchoring groups for new generation solar cells

Dye-sensitized solar cells (DSSC) have been the subject of constant attention in recent years thanks to the enhancement in their efficiency and stability. Metal-free D-?-A dyes are especially interesting, since their particular architecture allows a fine adjustment of their photo- and electrochemical properties. First, we modified the structure of already known dye DF15 by introducing two alkoxysilane (recently awarded to be one of the most stable and high-performing anchoring units for DSSC) by employing a Pd-catalyzed silylation reaction. Then, we altered the dye conjugate unit by replacing the central thiophene ring with a more electronrich ProDOT moiety, keeping the trialkoxyphenylsilyl anchor, with the aim to improve the dye light harvesting properties. The corresponding cyanoacrylic acid dye was also prepared for comparison. Finally, we analyzed the interfacial charge transfer processes taking place between the dyes and a nanocrystalline semiconductor (TiO2), by means of UV-Vis and IR transient absorption spectroscopy. The results obtained with the various anchoring groups were compared in order to study the different dynamics occurring in each case.