Blue solar panels, either dotting the landscape or rooftops, have fortunately become a familiar sight across the world. They conjure the image of a sustainable future where human civilization is no longer chained to dirty fossil fuels. To some people, however, solar panels are plain ugly. They just can’t stand those blue PV cells on their home or office rooftop; otherwise, they don’t have anything against them which is why these yet untapped customers comprise a market in itself.
Recognizing that some home owners and municipalities want more color options for their solar panels, a team of researchers has devised a clever way to imprint exist PV cells with silicon nanopatterns that scatter green light lending the whole panel a greenish appearance.
Now, colored solar panels aren’t exactly new. If you’ve been looking around, it’s likely you already saw red or even green panels. These, however, are simply painted with some special dyes and coatings that give a characteristic color but can significantly reduce efficiency in the process.
The literally green panels developed at the American Institute of Physics only lose 2 percent efficiency thanks to a smart design that employs soft-imprint lithography. The technique is akin to using a rubber stamp to imprint ink. In our case, the stamp imprints a dense array of silicon nanocylinders, each only 100 nanometers wide. Together, these nanocylinders work in tandem to create an electromagnetic resonance that scatters a particular wavelength of light. You can tune the wavelength of light by adjusting the cylinder array so the observer can get to see just about any color. For this particular demonstration, green was used.
“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, in a statement. “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.”
What’s more, the fabrication process can be adapted to existing production lines, the authors report in Applied Physics Letters. Again, it’s as easy as using an (oversized) stamp.
“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.”
Another added advantage is that, unlike dyed solar panels, the nano-stamped cells have 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,” Neder said.
Next, Neder and colleagues want to design imprints for red and blue solar cells. Once completed, they’ll have all the three primary colors which means the solar panels could be of virtually any color, even white. “Going to white is a really big step,” Polman said.