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• 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 agricultural waste as their raw material, claims 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 Centre for Biomedical Engineering. 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. But, now Mershin said 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 tenfold or so to become useful, he added.
• Mershin created a tiny forest of zinc oxide (ZnO) nanowires as well as a sponge-like titanium dioxide (TiO2) nanostructure coated with the light-collecting material derived from bacteria. The nanowires not only served as a supporting structure for the material, but also as wires to carry the flow of electrons generated by the molecules down to the supporting layer of material, from which it could be connected to a circuit. "It's like an electric nanoforest."
• "As a bonus, both zinc oxide and titanium dioxide—the main ingredient in many sunscreens—are very good at absorbing ultraviolet light. That's helpful in this case because ultraviolet tends to damage PS-I, but in these structures that damaging light gets absorbed by the support structure." "You can use anything green, even grass clippings as the raw material," he said. Because the system is so cheap and simple, Mershin hopes this will become a "way of getting low-tech electricity to people who have never been thought of as consumers or producers of solar-power technology." "Also, the instructions for making a solar cell will be simple enough to be reduced to one sheet of cartoon instructions, with no words."
• The only ingredient to be purchased would be chemicals to stabilise the PS-I molecules, which could be packaged inexpensively in a plastic bag. Essentially, Mershin said, within a few years a villager in a remote, off-grid location could "take that bag, mix it with anything green and paint it on the roof" to start producing power, which could then charge cell phones or lanterns. The research was funded in part by an unrestricted grant from Intel Corp., and also included researchers at the University of Tennessee.

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