Production and performance of a Photosystem I-based solar cell using nano-columnar TiO 2

To meet the world's growing energy demands in a renewable and cost-effective manner, Photosystem I has been studied as a model for solar energy capture. Previous work has demonstrated the ability to construct low cost biohybrid solar cells using Photosystem I and specialty surfactants onto metal oxide surfaces. Electrospray deposition has also been used for adsorption of plant proteins onto metal oxide surfaces. Attachment of Photosystem I onto nanostructured materials increases the surface area and activity of biohybrid solar cells. Recent work has shown that Photosystem I can be attached to metal oxide surfaces without using linkers and maintain high current density. However, the current density of the surface decreases over the course of weeks (unpublished data). This work investigated the performance of Photosystem I-based solar cells manufactured using electrospray deposition. Photosystem I was successfully deposited onto metal oxide surfaces, and current densities of up to 6.84 mA/cm 2 were measured. Different amounts of protein were deposited and the solar performance was tested for each cell. It was shown that very small and very large amounts of PS I increase the current density, but there is an intermediate regime where performance drops. This intermediate regime was attributed to a shading effect of the protein on the surface and self-assembly effects of the protein on the surface.