Research by Stanford engineers indicates that ricocheting light inside a polymer film of a solar cell behaves differently when the film is ultra thin. This nanoscale-thin film that has been roughed up can absorb more than 10 times the energy predicted by conventional theory.
Keeping sunlight in the grip of the solar cell long enough to get the maximum amount of energy from it by using a technique called “light trapping” is what helps to overcome the theoretical limit.
“The longer a photon of light is in the solar cell, the better chance the photon can get absorbed,” says Shanhui Fan, associate professor of electrical engineering. The efficiency of a material to absorb sunlight is important in determining the overall efficiency of solar energy conversion.
Nanoscale solar cells offer a savings in material costs because the organic polymer thin films and other materials are less expensive than silicon. Also, as they are nanoscale, the cells require much smaller quantities. In addition, the organic materials are manufactured in chemical reactions in solution instead of the high-temperature or vacuum processing needed for silicon manufacturing.