Eco-Friendly Sugar-Based Natural Deep Eutectic Solvents as Effective Electrolyte Solutions for Dye-Sensitized Solar Cells

Dye-sensitized solar cells containing sugar-based natural deep eutectic solvents (NADESs) as active electrolyte solvents have been studied in terms of their photovoltaic (PV) properties, including main PV characteristics, incident photon-to-current efficiency, and impedance properties. Five monosaccharides were selected as NADES H-bond donors and investigated with a phenothiazine-based sensitizer carrying a glucose functionality and a glucose-based co-adsorbent (glucuronic acid) to explore directional intermolecular interactions and to improve the PV performance. The highest power conversion efficiencies were recorded for cells containing the glucose-based sensitizer in the presence of glucuronic acid in the sugar-based NADES. When one of these components was omitted, performances were lower, suggesting that the best response came from an interplay between the sugar-based units. Not only has the unprecedented use of a NADES as a fully natural and bio-renewable dye-sensitized solar cell medium been presented, but for the first time an active role of the electrolyte solvent has been reported and exploited to increase the performance of the solar device.