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A dramatic and surprising magnetic effect of light discovered by University of Michigan researchers could lead to solar power without traditional semiconductor-based solar cells.
"The researchers found a way to make an optical 1 "said Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics.
Light has electric and magnetic components. Until now, scientists thought the 2 of the magnetic field were so weak that they could be ignored. What Rand and his colleagues found is that at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100 million times stronger than 3 expected. 4 these circumstances, the magnetic effects develop strength 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 5 goes into a material, gets absorbed and creates heat. Here, we expect to have a very low heat load. Instead of the light being absorbed, energy is stored in the magnetic moment. Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power 6 ." What makes this possible is a previously undetected brand of "optical rectification," says William Fisher, a doctoral student in applied physics. In traditional optical rectification, light"s electric field causes a charge separation, or a pulling 7 of the positive and negative charges in a material. This sets up a voltage, similar to 8 in a battery.
Rand and Fisher found that under the right circumstances and in right types of materials, the light"s magnetic field can also create optical rectification. The light must be shone through a 9 that does not 10 electricity, such as glass. And it must be focused to an intensity of 10 million watts per square centimeter. Sunlight isn"t this intense on its own, but new materials are being sought that would work at lower intensities, Fisher said.
"In our most recent paper, we show that incoherent light like sunlight is theoretically almost as 11 in producing charge separation as laser light is," Fisher said.
"This new 12 could make solar power cheaper, "the researchers say. They predict that with improved materials they could achieve 10 percent efficiency in 13 solar power to useable energy. That"s equivalent to today"s commercial-grade solar cells.
"To manufacture 14 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 15 . It"s already made in bulk, and it doesn"t require as much processing. Transparent ceramics might be even better."