In the search for more efficient solar cells, researchers in Japan have found that a recently discovered molecule, important in a plant’s ability to photosynthesise sunlight, could also reap rewards for solar cells.
Among photosynthetic pigments, chlorophyll is the most crucial one as it captures light energy and converts photons into electrons as a source of energy. While there are different types of chlorophyll molecules, one called ‘Chl f’ has only recently been discovered, with little known of its location or how it functions.
Now, researchers led by Prof Tatsuya Tomo from the Tokyo University of Science have published a study revealing new details about this mystery, with a discovery that could potentially help to make solar cells more powerful.
What the scientists knew so far was that Chl f is ‘far-red shifted’, which means that this molecule absorbs far-red light from the lower end of the light spectrum. By studying the alga where the molecule was first discovered, it was shown to be located at the periphery of one of two photosystems (photosystem I). A photosystem is a special structure that mediates photosynthesis.
‘Never been seen before’
They also found that far-red light causes structural changes in the photosystem, which are accompanied by the synthesis of Chl f in the algae, leading them to conclude that Chl f causes these structural changes in photosystem I.
This was the first finding to explain how the molecule works.
“This indicates that Chl f functions to harvest the far-red light and enhance uphill energy transfer,” Tomo said. “We also found that the amino acid sequence of photosystem I was altered so as to accommodate the structure of Chl f.”
Speaking of the importance of this discovery, Tomo said it could allow us to better mimic the process of photosynthesis in an artificial system to capture solar energy.
“About half of the solar energy that falls on the Earth is visible light, and the other half is infrared light,” he said.
“Our research puts forth a mechanism that can use light on the lower energy spectrum, which has never been seen before. Our findings show how to improve the efficiency of energy transfer in photosynthesis and, by extension, also provide important insights into artificial photosynthesis.”