New light harvesting technique by Stanford team may revolutionize solar industry

By James Maynard, Tech Times | February 18, 7:13 PM

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By studying the way photosynthesis works in bacteria, researchers hope to create a new generation of highly versatile solar cells. A study of one light-harvesting mechanism in materials examined the process of photosynthesis at the molecular level. The research was led by graduate student Hsiang-Yu Yang and Gabriela Schlau-Cohen of Stanford University.
(Photo : Elliott Brown)

Solar cells may see remarkable improvements to efficiency, thanks to a new research that has studied the way light harvesting systems handle photons. Implications of the research could include a leap in the efficiency of solar cells and collectors.

A study of one light-harvesting mechanism in materials examined the process of photosynthesis at the molecular level. The research was led by graduate student Hsiang-Yu Yang and Gabriela Schlau-Cohen of Stanford University.

"Through our approach, we are able to have a better understanding of the natural designs of light harvesting systems, especially how the same molecular machinery can perform efficient light harvesting at low light while safely dissipating excess excitation energy at high light," Yang said.

The study looks at the actions of various photosynthetic antenna proteins. Included among these was complex 2 (LH2), the primary antenna in purple bacteria. Researchers used an Anti-Brownian ELectrokinetic (ABEL) trap on the protein, which consists of just a single molecule.

Under low light, photosynthetic cells use photons to store energy in chemical form. When the organisms are exposed to excessive light, they dissipate that energy. By doing so, they prevent the formation of chemicals that could be harmful to the organism.

"By analyzing the transition between these states in a bacterial antenna protein, we found a process that may be one of the molecular mechanisms of photoprotection, or the way in which the organism protects itself from damage by excess light," Schlau-Cohen wrote.

How photosynthetic cells are able to absorb sunlight so efficently, and reject excess energy, has puzzled biologists for centuries. This process makes it possible for bacteria, algae and plants to thrive in wide environments around the world.

It also allows the being to collect energy regardless of weather conditions. On cloudy days, more energy is collected by the proteins, while excess energy is rejected when the shine shines. A similar system may be designed into artificial solar cells, making the devices more efficient.

Before that can happen, however, Hsiang-Yu and Schlau-Cohen need to see if a process like the one observed also occurs in higher plants. If a similar mechanism exists in green plants, it may provide the researchers a blueprint of how to design the systems artificially.

Solar cells have become far more efficent in the last few years. Commercial models are commonly found delivering electricity at 20 percent efficiency. Experimental models convert up to 30 percent of the sunlight that falls on them into electricity.

Details of the study was delivered at the 58th Annual Biophysical Society meeting in San Francisco on 16 February.

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