(262c) Integrating Photosystem I Proteins With Advanced Materials for Biologically Inspired Solar Energy Conversion

Photosystem I (PSI) is a ~10 nm protein complex that drives photosynthesis.  Because of its nanoscale size and photodiode-like properties, PSI has drawn a surging interest for use in biologically inspired energy conversion devices upon extracting it from plants and assembling it as films on electrode surfaces.  The research described in this presentation will focus on the molecular and electronic integration of spinach-extracted PSI at electrode surfaces, including metals, rectifying semiconductors, and graphene, to produce wet photoelectrochemical cells.  Specifically, I will describe how monolayers of PSI can be deposited onto electrodes using self-assembly and Langmuir-Blodgett/Schaefer methods as well as how multilayers of PSI are deposited through a vacuum-assisted drop-casting approach.  Thicker films of PSI absorb more light and yield much greater photocurrents as compared to monolayer films.  The electrode that these films are deposited on is vitally important for the performance of the film.  We have observed that micron-thick PSI films on p-doped silicon produce 200-times greater photocurrents than those obtained by deposition on gold. The position of the Fermi level combined with the band gap of silicon enables unidirectional electron transfer to PSI so that we avoid current cancellation from non-optimally aligned proteins.  Adsorption of PSI on graphene provides flexibility in cell design due to the conductive, transparent nature of the atomically thin electrode.  Furthermore, integrating a PSI film with reduced graphene oxide improves film conductivity and enhances observed photocurrents.  These discoveries are leading to vastly improved performances for PSI-biohybrid solar cells.