Don’t Eat Your Spinach: Nature Inspired Biohybrid Solar Cells

EPA Grant Number: SU835287
Title: Don’t Eat Your Spinach: Nature Inspired Biohybrid Solar Cells
Investigators: Jennings, G. Kane , Anilkumar, Amrutur V.
Institution: Vanderbilt University
EPA Project Officer: Lank, Gregory
Phase: II
Project Period: August 15, 2012 through August 14, 2014
Project Amount: $88,992
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2012) Recipients Lists
Research Category: P3 Challenge Area - Energy , P3 Challenge Area - Materials & Chemicals , Pollution Prevention/Sustainable Development , P3 Awards , Sustainability


Our team will work to design and develop solar panels where the active components for solar conversion are nanoscale photosynthetic proteins (Photosystem I (PSI)) harvested from spinach and other green plants. In Phase II, we propose to build both on the scale up strategies our design team developed in Phase I and also a new result from the research team, to scale up a second generation biohybrid solar cell that promises to yield greatly enhanced solar conversion performance.


First, we will extract PSI from other sources beyond spinach, including rapidly growing, non-food-based plants such as kudzu. Developing PSI films from a non-food plant would lessen any impact that biohybrid solar cells, assuming an ultimate large-scale production, would have on food supply. Second, we will optimize the PSI film thickness to maximize power generation on the new substrates. In general, thicker PSI films provide greater photocurrents because they absorb more of the incoming light, until a critical thickness is reached when light can no longer penetrate the film and reach the underlying substrate. Third, we will identify the most effective mediator for this new PSI/semiconductor system and fine tune its concentration. The mediator must accept electrons from PSI at a sufficiently high potential that it can rapidly deliver those electrons to a counter electrode. Fourth, we will investigate whether conductive additives within the PSI film aid in electron transfer and overall photocurrent output. The system of chlorophyll molecules surrounding each PSI protein provides some conductivity within the PSI films for rapidly transferring electrons, but boosting this transfer rate through additives could greatly enhance photocurrents and efficiencies. Fifth, we must scale up the individual cell to modules and panels. This scale up will be guided by the cell/module/panel assembly strategies developed in Phase I but applied to a different cell design.

Expected Results:

We have very recently demonstrated 850 μA/cm2 photocurrent densities from our PSI films by swapping the gold electrode with an appropriate semiconductor. This current density is ~400-fold larger than that produced by our first-generation cell that has spurred this Phase I project and is larger than any photocurrent ever reported for PSI-based systems, pushing toward the mA/cm2 range that is typical of mature silicon-based photovoltaics. Successful scaleup of this technology would amplify our power over previous devices.

Supplemental Keywords:

photosynthesis, photoelectrochemical, silicon

Relevant Websites:

Phase 1 Abstract

P3 Phase I:

Don’t Eat Your Spinach: Nature Inspired Biohybrid Solar Cells  | Final Report