Light ricocheting around inside the polymer of film of a solar cell behaves differently when the film is ultra thin. If that film is nanoscale-thin and has been roughed up, it can produce 10 times more energy, according to a study published in Proceedings of the National Academy of Sciences.
Using light trapping, more energy can be harvested from solar power, writes the Stanford Report.
“The longer a photon of light is in the solar cell, the better chance the photon can get absorbed,” Associate Professor of Electrical Engineering at Stanford University, Shanhui Fan, told the Stanford Report.
Light trapping is already used in silicon solar cells, but efficiency gains seem to reach a limit. However, light behaves different in thinner films;
Fan explained: “We all used to think of light as going in a straight line. For example, a ray of light hits a mirror, it bounces and you see another light ray. That is the typical way we think about light in the macroscopic world.
“But if you go down to the nanoscales that we are interested in, hundreds of millionths of a millimetre in scale, it turns out the wave characteristic really becomes important,” he told the Stanford Report.
Postdoctoral Researcher Yongfu Yu, added: “The amount of benefit of nanoscale confinement we have shown here is really surprising. Overcoming the conventional limit opens a new door to designing highly efficient solar cells.”
The researchers sandwiched the organic solar thin-film between cladding layers. Atop the cladding layer, a patterned rough-surfaced layer was placed, designed to send the incoming light off in different directions when entering the solar thin-film.