Science News Story

Blackberries and Spinach may be the Secret to Solar Energy Efficiency

Blackberry juice seems to be the ingredient needed to enhance the electrical output of spinach-derived biohybrid solar cells. Experiments show that combining dye from blackberries and molecules extracted from spinach increases the energy solar cells can capture and store.

Professor Kane Jennings and Professor David Cliffel at Vanderbilt University in Nashville, Tenn., conducted a series of biomolecular experiments to incorporate natural materials in biohybrid solar cells with the hopes of increasing the cells’ voltage. Biohybrid solar cells may hold the key to better energy in the near future. Scientists have long known that the sun supplies a better, more sustainable source of energy than many of the prevalent resources used today such as coal, wood, and corn. However, the big challenge facing many researchers is how they can effectively obtain and store solar energy for human use.

Capturing energy from the sun then converting it into a power source is a fiscally demanding process. Economic viability concerns many scientists these days. Even if an experiment produces positive results or showcases the best possible way to achieve a scientific feat, if it cannot be done in a financially responsible way researchers will likely not pursue it. “A goal of researchers in the solar area is to design solar cells that can produce high power but also those that can be affordably scaled up to larger areas,” says Jennings whose research focuses on optimizing molecular design. The biohybrid solar cells he and Professor Cliffel studied provide an effective method for generating significant power at a low cost.

Cost is not the only factor solar energy researchers must consider. Biohybrid solar cells transfer energy in units of photovoltage and photovoltage is color dependent. Thanks to unsuccessful experiments conducted by previous scientists utilizing various other dyes, Jennings and Cliffel hypothesized blackberry juice-derived dye, anthocyanin, would be the one that worked. Anthocyanins are used for fabric dying and food coloring in dark reds, purples, blues and black. When combined with photosynthetic molecules extracted from spinach, they absorb complimentary wavelengths of light from the sun and convert the light energy to chemical energy.

In order to facilitate the solar energy capture and storage process, the blackberry and spinach duo is layered onto a titanium oxide coated, microscopic gold electrode. Researchers then place the electrode in the presence of simulated sunlight and measure the voltage output over time. Jennings and Cliffel’s experiments yielding photovoltage twice that of anthocyanins on their own, and twenty times what spinach extracts were able to produce alone.

According the Jennings, this shows how important a biohybrid, multidisciplinary approach to solar energy solutions truly is. “The work we do requires a fusion of different fields, including surface chemistry, electrochemistry, biochemical engineering, materials science, and electrical engineering.  Therefore, the collaboration between my group in Chemical and Biomolecular Engineering and that of Professor David Cliffel in Chemistry has been very beneficial to make progress and advance the field,” says Jennings.

Professor Jennings cannot say which dyes they are looking to test next, but don’t be surprised if it comes from yet another food you can find in the produce aisle.