There are a lot of things to like about solar power. It helps the world kick the fossil fuel habit, it’s clean and plentiful, and leaves no carbon footprint. But it needs the sun to work, which makes it less practical in places where overcast days are common.
A genetically engineered bacterium that uses dye to convert light to energy ultimately might change that. Scientists in British Columbia — which often has cloudy days — have built a cheap, sustainable solar cell from E. coli, creating a “biogenic” solar cell — so named because it is made of a living organism. Theirs is not the first experimental biogenic solar cell, but it’s different from the others — and it produced a more powerful current, they said. Also, it works as well in dim light as in bright light.
Any material that can be “excited” or energized sufficiently by light to release electrons can be used in solar cells to generate electricity. In biogenic solar cells, the material “excited” by light is biological — in this case, the dye — compared to conventional, or inorganic, solar cells which use crystalline silicon to generate electrons.
“British Columbia aspires to be one of [the] leading de-carbonized economies of the world,” said Vikramaditya Yadav, a professor in the University of British Columbia’s department of chemical and biological engineering. “Reliable generation and supply of clean energy is key to achieving this objective, and solar energy is a leading candidate for de-carbonization of the energy sector. However, BC’s typically dreary winter skies impose unique requirements on the photovoltaic materials to be used for harnessing solar energy.”
Previous attempts to build biogenic solar cells have focused on extracting the natural dye that bacteria use for photosynthesis. This is an expensive and complicated process that uses toxic materials and actually can harm the dye. The Canadian researchers decided to try something a little different. They left the dye in the bacteria, and tinkered with the organism, inducing it to produce large amounts of lycopene, the same dye found in tomatoes and other red fruits.
They then coated the bacteria with a mineral that acts as a semiconductor, and applied the mixture to a glass surface. With the coated glass on one end of the cell acting as an anode—an electrode through which conventional current flows — they generated a current density much greater than that achieved by others in the field. (0.686 milliamps per square centimeter compared with the 0.362.) ...
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