Using Fruit to Aid the Sun's Work

Developing New Ways to Extract Low-Cost Materials for Organic Solar Cells

Blackberries, blueberries, oranges and grapes: chemistry students at Rowan University are loading up on their fruits these days, but it has nothing to do with the food pyramid. The students are using the fruit to produce solar energy — or more precisely, to create solar cells, under the guidance of Dr. Darius Kuciauskas, an assistant professor of chemistry.

“To develop efficient — and most importantly, inexpensive — solar cells, scientists are following the design of photosynthetic systems,” the professor says. “Research on so-called ‘third-generation’ solar cells is being carried out at Rowan University.”

He explains that commercially available solar cells — such as the ones people can put on their roofs — are “first generation” solar cells. They are based on crystalline silicon, and they are expensive. “Second-generation” solar cells are also based on crystalline semiconductors, but use only thin films of the material. “Third-generation” solar cells are still in the research stage and some years away from wide commercial use. There are several different designs under this umbrella, including Rowan’s “dye-sensitized solar cells,” which were invented by a chemist in Switzerland. The idea of the “third-generation” field is to use inexpensive material — like paint — assembled into well-defined biomimetic structures that are manmade but mimic nature.

The Rowan researchers are refining a process in which they extract dye from a range of fruits and blend it into a kind of scientific “smoothie.” They separate out the heavy particles using filters and a centrifuge to obtain a liquid, which they freeze dry. The novel process, designed by the Rowan research team, leaves the researchers with sugar and a dye. They separate the components and obtain pure, brightly colored dyes in an acidic solution.

From there, they place the dye on a conductive glass coated with a porous film of titanium dioxide — a material found in everything from toothpaste to sandwich cookies to white paint — which bonds the dye to the glass. Finally, they add iodine and potassium iodide electrolyte for dye regeneration.

When light hits the processed fruit dye on the glass, it “excites” the electrons, which mobilizes or “frees” them. The electrons travel to a conductive glass electrode. That, in turn, produces electricity. While the output from these organic cells is less than that from traditional silicon cells, it has the advantage of using very inexpensive, store-bought materials.

The Petroleum Research Fund of the American Chemical Society will support future solar energy research at Rowan University.

Back to top