Solar Cells Don’t Grow on Trees … Or Do They?

Thin film solar cells are lightweight and flexible, but are often made from materials that aren't quite eco-friendly. Researchers at Georgia Tech and Purdue have produced organic PV cells attached to plant-based cellulose nanocrystal substrates, which can be recycled at the end of their lifespans. This process could decrease both the cost and the environmental footprint of solar cells.

Solar cells are semiconductors, and as such, their production isn’t exactly environmentally-friendly. It’s not as bad as some solar skeptics would have you believe – it takes one to three years for a photovoltaic (PV) panel to generate enough energy to offset the carbon footprint of making the panel itself. Still, it would be nice if they could be made with a cleaner process.

Researchers at Georgia Institute of Technology and Purdue University have created polymer photovoltaic cells attached to transparent cellulose nanocrystal substrates derived from plant matter, enabling the solar cells to be produced from inexpensive organic materials. But don’t worry about deforestation resulting from PV panel production – the process works with almost any plant matter, including byproducts like sawdust and grass clippings. As an added bonus, the cells are water soluble, so they can be easily recycled at the end of their lifespans. And no, they won’t melt in the first rainstorm; they’ll be covered with an eco-friendly protective coating. Here’s what one looks like:

Image: Georgia Tech Center for Organic Photonics and Electronics

The cells that they created are only 2.7% efficient, roughly one-fifth of a commercial PV panel today. Still, it’s much higher than other cells produced with organic materials. Georgia Tech Professor Bernard Kippelen, who led the study, says, “Our next steps will be to work toward improving the power conversion efficiency over 10 percent, levels similar to solar cells fabricated on glass or petroleum-based substrates.” He suggests that further optimizations may produce cells with an efficiency that rival glass-mounted silicon PV cells.

It seems unlikely to me that these organic cells will replace the rigid PV panels that we see on rooftops and solar farms. Even though I’m confident that they’ll improve the efficiency of organic PV devices, semiconductor-based PV cells are also showing improvements. Still, it’s good to see inexpensive, eco-friendly materials being added to the PV arsenal. While solar farms and rooftops might continue to use rigid PV panels, those applications have longer lifespans. Organic PV cells can be used to power devices with expected lifespans of 5 years or less and where lightweight flexible PV cells are needed. Does anyone expect to use their current cell phone for the next 25 years? Didn’t think so.

So here’s a question for product designers and consumers: where do you see organic PV cells fitting into the energy-production world?