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Stromatolites From Australia Give Clues on Infrared Light Harvesting for Solar Cells

Stromatolites in Western Australia

If we learned to fly from birds, and to swim from fish, then why shouldn’t we learn to extract our energy like some plants do? The Australian Shark Bay gives us a clue on how we could.

Min Chen, a researcher from the University of Sidney, helped by her colleagues, recently discovered that stromatolites living there actually use infrared light as their source of energy.

Being considered one of the most primitive life forms with an age of more than 3.4 billion years, stromatolites are built up by sediment-trapping cyanobacteria. An evolutionary logic says that because when animals appeared and ate the algae from the surface of waters, stromatolites adapted and now they live only where algae-eating animals don’t – the very salty waters of Shark Bay.

The cyanobacteria that make up the stromatolites only receive infrared light because of the bulky sediments around them, so they evolved into efficient infrared light-trapping organisms over time. The chlorophyll they use – chlorophyll f – is made by a previously unstudied and yet unnamed bacterium.

On the other hemisphere, Shuguang Zhang from MIT finds uses for the newly discovered clorophyll in making better solar cells by using it directly. Having made spinach-based solar cells before, Zhang sets up a photosystem featuring chlorophyll molecules and anchors it to a semiconductor nanowire that transfers the electrons displaced by the photons hitting the photosystem into a metal. Thus he generates an electric current.

But Zhang is not alone. Helped by Michael Grätzel, the inventor of dye-sensitized solar cells, he explores ways to use infrared-trapping cyanobacteria photosystems instead of the inorganic molecular dyes Grätzel had developed earlier.

It’s still premature to say whether this is the best approach, but for sure such a discovery, which is not only important from an evolutionary point of view, but also a lesson from nature, will succeed getting its deserved place among those we have learned for millennia.

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