Organic sensitizers featuring tetrathienosilole core for efficient and robust dye-sensitized solar cells

Siloles are one of the most promising building blocks for the construction of functional materials that exhibit potential application in organic photovoltaic. In the present work, two novel organic dyes featuring highly conjugated and planar tetrathienosilole (TTS) as n-bridge have been successfully synthesized and employed in dye-sensitized solar cells (DSSCs) for the first time. For comparison, dye W13 with non-rigidified 2,2 '-bithieno [3,2-b]thiophene linker was prepared as well. The effects of n-bridge rigidification upon the optoelectronic properties as well as the charge transfer energetic and kinetic features of these dyes have been systematically researched. It was found that a significant enhanced open-circuit voltage had been displayed for TTS-based sensitizers as the rigidification of n-bridge with tetrahedral silicon atom. Moreover, the energy levels alignment of the dyes could be fine-tuned through modulating the electron-donating groups to optimize the dyes regeneration process. Under AM 1.5G irradiation, the devices fabricated by W15 employing [Co(phen)3]2+/3+ electrolyte achieve the highest power conversion efficiency of 8.10%, which is about 19% higher than that of W13, demonstrating the great potential of TTS spacer for constructing highly efficient organic sensitizers for DSSCs.