Application of Photosystem I Multilayer Films for Photovoltage Enhancement in Aqueous Natural Dye Sensitized Solar Cells

Among the photosynthetic proteins, Photosystem I (PSI) is notable for achieving the most energetic reduction potential in nature and for its outstanding internal quantum efficiency. Stimulated by absorption of indigo, blue, and red photons, PSI facilitates electron excitation and sub-microsecond cross-membrane transport, all while retaining 1.1 eV of absorbed energy. As such, PSI is a model photodiode and the subject of broad scientific study and engineered emulation. In this study, we report photovoltage enhancement through application of PSI multilayer films atop TiO­₂ anodes loaded with the natural dye cyanidin-3-glucoside—extracted from blackberries—and mediated by an aqueous Fe(CN)₆^4-/3- redox shuttle. The enhancement phenomena is found to be dependent on both the amount of PSI deposited on the surface as well as the concentration of reduced redox group present in the electrolyte solution. We attribute the effect to PSI’s photocatalytic reduction of photogenerated oxidized redox species in solution, which attenuates recombination rates at the dye/electrolyte interface. The blue and red absorption bands of PSI’s light harvesting chlorophylls complement the strong green absorption of the sensitizing dye, allowing for better utilization of the visible spectrum.