Bacteria-based solar cell operates in low light

July 05, 2018 // By Nick Flaherty
Researchers at the University of British Columbia have built a solar cell that uses bacteria for the energy conversion and operates in low light conditions.

The biogenic cell generated a current stronger than any previously recorded from such a device, and worked as efficiently in dim as in bright light.

"Our solution to a uniquely B.C. problem is a significant step toward making solar energy more economical," said Vikramaditya Yadav, a professor in UBC's department of chemical and biological engineering who led the project. "We recorded the highest current density for a biogenic solar cell," said Yadav. "These hybrid materials that we are developing can be manufactured economically and sustainably, and, with sufficient optimization, could perform at comparable efficiencies as conventional solar cells."

Previous efforts to build biogenic solar cells have focused on extracting the natural dye that bacteria use for photosynthesis. This is a costly and complex process that involves toxic solvents and can cause the dye to degrade.

Instead the UBC researchers genetically engineered E. coli bacteria to produce large amounts of lycopene, a dye that gives tomatoes their red-orange colour and is particularly effective at harvesting light for conversion to energy. The researchers coated the bacteria with a titanium dioxide to act as a semiconductor, and applied the mixture to a glass surface.

With the coated glass acting as an anode at one end of their cell, they generated a current density of 0.686 milliamps per square centimetre, an improvement on the 0.362 achieved by other teams. The cell absorbs mostly n the UV region at 450, 475 and 505nm and the higher output allows energy conversion in lower light conditions.

The cost savings are difficult to estimate, but Yadav believes the process reduces the cost of dye production to about 10% of other processes. The drawback is that the bacteria die as a result, so the holy grail, says Yadav, would be finding a process that doesn't kill the bacteria, so they can produce dye indefinitely.

He added that there are other potential applications for these biogenic materials in mining, deep-sea exploration and other low-light environments.

www.ubc.ca

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