Low-cost photovoltaic panels from plant material may be alternative to traditional solar cells

Within a few years, people in remote villages in the developing world may be able to make their own solar panels, at low cost, using otherwise worthless agricultural waste as their raw material.

That's the vision of MIT researcher Andreas Mershin, whose work appears this week in the open-access journal Scientific Reports. The work is an extension of a project begun eight years ago by Shuguang Zhang, a principal research scientist and associate director at MIT's Center for Biomedical Engineering. Zhang was senior author of the new paper along with Michael Graetzel of Switzerland's École Polytechnique Fédérale de Lausanne.

In his original work, Zhang was able to enlist a complex of molecules known as photosystem-I (PS-I), the tiny structures within plant cells that carry out photosynthesis. Zhang and colleagues derived the PS-I from plants, stabilised it chemically and formed a layer on a glass substrate that could - like a conventional photovoltaic cell - produce an electric current when exposed to light.

But that early system had some drawbacks. Assembling and stabilising it required expensive chemicals and sophisticated lab equipment. What's more, the resulting solar cell was weak: Its efficiency was several orders of magnitude too low to be of any use, meaning it had to be blasted with a high-power laser to produce any current at all.

Now Mershin says the process has been simplified to the point that virtually any lab could replicate it - including college or even high school science labs - allowing researchers around the world to start exploring the process and making further improvements. The new system's efficiency is 10,000 times greater than in the previous version - although in converting just 0.1 per cent of sunlight's energy to electricity, it still needs to improve another ten-fold or so to become useful, he says.

The key to achieving this huge improvement in efficiency, Mershin explains, was finding a way to expose much more of the PS-I complex per surface area of the device to the sun. Zhang's earlier work simply produced a thin flat layer of the material; Mershin's inspiration for the new advance was pine trees in a forest.