Researchers at the University of Michigan have discovered a way to make an “optical battery” that generates power from the magnetic components of a light beam.
This surprising discovery could eventually rival or replace the traditional semiconductor-based solar cell, according to Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics.
It already has overturned a century-old tenet of physics.
“You could stare at the equations of motion all day and you will not see this possibility. We’ve all been taught that this doesn’t happen,” said Rand, an author of a paper on the work published in the Journal of Applied Physics. “It’s a very odd interaction. That’s why it’s been overlooked for more than 100 years.”
Light has electric and magnetic components. Until now, scientists thought that the magnetic attributes of light were so weak that they could be ignored. What Rand and his colleagues found is that when light is at the right intensity and is traveling through a material that does not conduct electricity—such as glass—it can generate magnetic effects that are 100 million times stronger than previously expected. These magnetic effects are equivalent to a strong electric effect.
“This could lead to a new kind of solar cell without semiconductors and without absorption to produce charge separation,” Rand said. “In solar cells, the light goes into a material, gets absorbed, and creates heat. Here, instead of the light being absorbed, energy is stored in the magnetic moment.”
Intense magnetization can be induced by intense light—10 million watts per square centimeter —and then it is ultimately capable of providing a capacitive power source.”Sunlight (News - Alert) isn’t this intense on its own, but new materials are being sought that would work at lower intensities, said William Fisher, a doctoral student in Applied Physics.
This new technique could make solar power cheaper, the researchers say. They predict that, with improved materials, they will be able to achieve 10 percent efficiency in converting solar power to useable energy. That’s equivalent to today’s commercial-grade solar cells.
“To manufacture modern solar cells, you have to do extensive semiconductor processing,” Fisher said. “All we would need are lenses to focus the light and a fiber to guide it. Glass works for both. It’s already made in bulk, and it doesn’t require as much processing. Transparent ceramics might be even better.”
In experiments this summer, the researchers will work on harnessing this power with laser light, and then with sunlight.
The paper is titled “Optically-induced charge separation and terahertz emission in unbiased dielectrics.” The university is pursuing patent protection for the intellectual property.
For more information, visit the University of Michigan website.
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Edited by Carrie Schmelkin