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

As one of the most promising classes of third-generation PV technologies, 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 (characterized by donor (D) and acceptor (A) moieties joined by a conjugated unit) are especially interesting, since their particular architecture allows a fine adjustment of their photo- and electrochemical properties. In this work, four new D-?-A dyes for DSSCs were synthesized. First, we introduced an electronrich ProDOT moiety in the conjugated unit of a traditional DSSC dye (named D5) to increase the light-harvesting efficiency of the structure (1). Then, we explored the possibility to improve the stability of the dye on the semiconductor by using the alkoxysilane group, recently awarded to be one of the most stable anchoring units for DSSC (2). We changed the corresponding cyanoacrylic acid (3 and 4 are obtained from the acid DF15) and the length between the dyes and the semiconductor surface in order to verify the difference between them. Finally, we analyzed the interfacial charge transfer processes taking place between the dyes and a nanocrystalline semiconductor (TiO2), by meanso 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.