Green silicon solar minimodule (0.7 x 0.7 sq.-cm) Credit: AMOLF

Existing black and blue solar panels, which are ubiquitous on roofs nationwide, are not aesthetically pleasing. If they were more colorful, architects, city planners, and homeowners might use them more. Now, we might have better-looking panels.

A group of researchers at the Physics Research Center AMOLF in the Netherlands just published the result of a study in Applied Physics Letters, claiming that they have developed a method to imprint existing solar panels with silicon nanoparticles that reflect green light. The painted panels lose only 10 percent of their efficiency (about two percent of the total efficiency) and have a green appearance from most angles.

"Some people say 'Why would you make solar cells less efficient?' But we can make solar cells beautiful without losing too much efficiency," said Verena Neder, a researcher at AMOLF and lead author of the paper. "The new method to change the color of the panels is not only easy to apply but also attractive as an architectural design element and has the potential to widen their use."

Integrated Mie scattering designs for colored solar panels. (a) and (b) Schematic of silicon nanoscatterer arrays on top (a) and bottom (b) of a sapphire cover slide, integrated into a silicon heterojunction solar module using immersion oil. (c) Top-view SEM image of a square array of silicon nanoscatterers on a sapphire cover slide, made by SCIL. (d) SEM image of a cross section of the silicon nanoscatterers on Sapphire made using focused ion beam milling. Credit: AMOLF

The bright green solar panels were created through soft-imprint lithography to imprint a dense array of nanocylinders of about 100 nanometers wide. Each nanocylinder is designed to scatter a particular wavelength that is determined by the geometry of the nanocylinder, using Mie Scattering. In addition, the technique can be fine tuned to change the color of the panel to any color.

"In principle, this technique is easily scalable for fabrication technology," said Albert Polman, a scientific group leader at AMOLF and senior author on the paper. "You can use a rubber stamp the size of a solar panel that in one step, can print the whole panel full of these little, exactly defined nanoparticles. Unlike existing colored solar panels, the nanopatterns give a consistent appearance from different angles. "The structure we made is not very sensitive to the angle of observation, so even if you look at it from a wide angle, it still appears green," he adds.

An abstract of the publication can be found here.