Nanotextures created with designs similar to those found in the eyes of moths could help researchers develop a new generation of solar panels. These unique layers work by preventing reflections of the light off their surfaces, thereby converting a greater percentage of sunlight into energy than is possible with current manufacturing technologies.
Solar cells traditionally use various coatings to help reduce reflections, in order to increase efficiency of the devices.
Brookhaven National Laboratory researchers developed a nanoscale texture, in which the material itself provides anti-reflection capabilities similar to high-quality optical coatings. In mass production, eliminating the need for coatings could streamline manufacturing, reducing the cost of the green energy collectors.
"The issue with using such coatings for solar cells, is that we'd prefer to fully capture every color of the light spectrum within the device... But each color of light couples best with a different antireflection coating, and each coating is optimized for light coming from a particular direction. So you deal with these issues by using multiple antireflection layers. We were interested in looking for a better way," Charles Black from Brookhaven Lab's Center for Functional Nanomaterials (CFN), said.
Moths eyes feature a myriad of tiny "posts" which help capture light, providing the insects with increased night vision. Each of these structures is smaller than a wavelength of light. The design also prevents eyes of the tiny animals from glowing in reflected light, giving away their presence to predators.
Nanotextures inspired by moth eyes could also be used to enhance the brightness of light-emitting diodes (LED's), to provide radar-absorbing shells for military vehicles, or to reduce glare in lenses or windows.
Reflections often occur in optics where light moves from one material - such as glass - to another medium, including air. Different materials possess different refractive indexes, and coatings with ratings between those of two transition mediums can help "ease" travel of photons through the system.
A black copolymer was applied to the surface of a silicon solar cell, which then self-organized into minuscule structures, forming a template of formations able to capture sunlight. A plasma of reactive gases was then used to form a layer of posts covering the cell. Similar methods are used in the manufacture of semiconductors.
"Adding these nanotextures turned the normally shiny silicon surface absolutely black," Atikur Rahman, a researcher at CFN, stated in a press release.
A thin layer of silicon oxide, which naturally forms when silicon is exposed to air, was found to benefit the new technology.
Development of the new anti-reflection technology was detailed in the journal Nature Communications.