Alkoxysilane anchoring groups for third generation solar cells: new synthetic methods and transient absorption spectroscopy analysis

Dye-sensitized solar cells (DSSC) have been the subject of constant attention in recent years for their potential as novel PV technology, which led to the enhancement in their efficiency and stability. Among the sensitizers, metal-free D-?-A dyes are especially interesting, since their particular architecture allows a fine adjustment of their photo- and electrochemical properties. Our work focused on developing new synthetic methods to insert the alkoxysilane anchoring group, recently recognized as one of the most stable and high-performing anchoring units for DSSC. First, we studied the insertion of two different spacers for the silicon-based moiety on the structure of already known dye DF15. Then, we altered the dye conjugate unit by replacing the central thiophene ring with a more electronrich ProDOT moiety with the aim to improve the dye light harvesting properties and explored a different way to insert the trialkoxyphenylsilyl anchor. The corresponding cyanoacrylic acid dye was also prepared for comparison. Finally, we analyzed the photochemical properties of the dyes in different solvents and the interfacial charge transfer processes taking place between them and a nanocrystalline semiconductor (TiO2), by means of transient absorption spectroscopy. The results obtained with the various anchoring groups were compared in order to study the different dynamics occurring in each case.