Researchers have found that etching a nanoscale texture onto silicon material creates an antireflective surface that could make solar cells more efficient. The new method was inspired by the eyes of moths.
Reducing the amount of sunlight that bounces off a solar cell could increase the conversion of sunlight to electricity, and this new technique could help scientists achieve that, Brookhaven National Laboratory reported.
"For antireflection applications, the idea is to prevent light or radio waves from bouncing at interfaces between materials," said physicist Charles Black, who led the research at Brookhaven Lab's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility.
In order to control reflectivity one must control the "refractive index," which influences how waves of light propagate through the material. Adding a coating with an intermediate refractive index where two materials meet helps lower the reflectivity.
"The issue with using such coatings for solar cells," Black said, "is that we'd prefer to fully capture every color of the light spectrum within the device, and we'd like to capture the light irrespective of the direction it comes from. 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."
The researchers turned to moths for inspiration because they have antireflective eyes due to patterns of tiny "posts" that are smaller than wavelengths of light. These fascinating eyes improved the moth's night vision and prevented predators from detecting them by their glowing eyes.
In order to replicate the moths' eyes the team coated the top surface of a silicon solar cell with a polymer material called a "block copolymer." The new technique proved to change the refractive index of the material and cut down its reflective nature.
"We are working to understand whether there are economic advantages to assembling silicon solar cells using our method, compared to other, established processes in the industry," Black said.
The findings were published in a recent edition of the journal Nature Communications.
