Because moths need to use every little bit of light available in order to see in the dark, their eyes are highly non-reflective. This quality has been copied in a film that can be applied to solar cells, which helps keep sunlight from being reflecting off of them before it can be utilized. Now, a new moth eye-inspired film may further help solar cells become more efficient.
The film, developed at North Carolina State University by a team led by Dr. Chih-Hao Chang, is designed to minimize “thin-film interference” in thin film solar cells.
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Thin-film interference is what causes gasoline slicks on water to take on a rainbow-colored appearance. Some sunlight is reflected off the surface of the clear gasoline, while some more penetrates its surface, but then is reflected back up through it by the surface of the underlying water. Because the two sources of reflected light have different optical qualities, they interfere with one another when combined – thus the rainbow effect.
The same sort of phenomenon can occur when any thin, transparent films are placed together. In the case of thin-film solar cells, which are made up of layered films, some of the sunlight is effectively lost at every film-to-film interface where the interference occurs.
To keep this from happening, Chang’s team created films with built-in cone-shaped nanonostructures, similar to those found on moths’ eyes. When present on the surface of one film, these structures are able to penetrate into the underside of a film laid over top of it, meshing them together almost like Lego pieces. As a result, much less in the way of thin film interference occurs between the two. This process could be repeated as several films are layered one on top of the other.
According to the scientists, the amount of light reflected by one of these nanostructured interfaces is one one-hundredth the amount reflected by a regular film-to-film interface. They now plan on using the technology in a solar device, with an eye towards commercial applications.
A paper on the research was published this week in the journal Nanotechnology.
Source: North Carolina State University