Photosystem I (PSI) is one of the key reaction centers of photosynthesis, a protein-pigment super-complex that converts light energy to chemical potential energy with a quantum efficiency approaching 100%. PSI has demonstrated the ability to serve as the photosensitizer in biohybrid dye sensitized solar cells (DSSCs). DSSCs consist of three major components: a photosensitive dye adsorbed onto a TiO2 semiconductor, a counter electrode, and a redox mediator. The functionality and efficiency of the cell are dependent on the HOMO/LUMO band-gap of the dye, the conduction band of the semiconductor, and the redox potential of the mediator. The traditional I-/I3- redox couple is corrosive to proteins, has a redox potential similar to that of PSI, and absorbs light in the visible spectrum making it unsuitable for a PSI-based solar cell. Current research has focused on cobalt complexes as a redox mediator in biohybrid solar cells as they are not corrosive and offer more negative redox potentials, resulting in a greater driving force for the rereduction of PSI. Herein, the synthesis and characterization of an alkyl substituted benzyliminodiacetic acid complex and 1,10-dihydroxyphenanthroline complex are presented. As cobalt complexes are primarily soluble in acetonitrile, ligands which bear polar functional groups were chosen to improve aqueous solubility, a more suitable solvent system for PSI. Ultraviolet-visible absorption difference spectra, solubility tests, fluorescent studies, PSI rereduction kinetics and photocurrent data for these complexes will be presented as well.

Cobalt redox mediators for integration in photosystem I biohybrid solar cells

255th National Meeting (2018)

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