Researchers at the University of British Columbia have demonstrated a new and inexpensive approach to developing solar cells that use bacteria to convert light into energy. The cells, which produce a current that is stronger than previously recorded from this type of device, and which operate just as effectively in low light as bright, could become as efficient as synthetic cells in standard solar panels and lead to more economical solar energy.
As described in the journal Small [Srivastava et al. Small (2018) DOI: 10.1002/smll.201800729], rather than use electronics, these solar cells are “biogenic” as they are made of living organisms. While past attempts to develop biogenic solar cells have explored ways of extracting the natural dye that bacteria need for photosynthesis, this is an expensive and difficult procedure requiring toxic solvents, and can degrade the photosynthetic chemicals. However, the new approach reported here involved leaving the dye in the bacteria.
“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”Vikramaditya Yadav
Many bacteria have already been shown to convert sunlight into energy using photosynthesis due to a chemical produced by the bacteria. This research used genetically engineered E. coli bacteria to produce large amounts of lycopene, a dye that is especially efficient at harvesting light for conversion to energy. On coating the bacteria with a mineral to act as a semiconductor to produce electricity, the team then applied the mixture to a glass surface.
The coated glass acts as an anode at one end of the cell, generating a current density of 0.686 milliamps per square centimetre, almost double that shown in similar studies. As project leader Vikramaditya Yadav said, “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”.
The photosynthetic chemicals used by the E. coli are just as effective in low light or cloudy skies as in direct sunlight, and could lead to greater adoption of solar energy in regions that tend to lack sunshine, as well as applications in low-light environments such as mining and ocean exploration. The research could also help the development of bio-photovoltaic materials and organic optoelectronics that are environmentally friendly, cheap and straightforward to manufacture. The team hope the process will significantly lessen the expense of producing dye, and are keen to improve the cell design further, as well as to identify a process that doesn't kill off the bacteria so that the dye could perhaps be produced indefinitely.