A common sight in the forests and meadows of India is the common rose butterfly. Known for its velvety black wings and colorful body and tail, the common rose spends its day gathering nectar from flowers like zinnias and Egyptian Starcluster. But soon, the common rose might be known for something else—making our solar panels more efficient.
“I was in a conference and somebody was presenting about butterflies and their nanostructures, and I was intrigued,” says Radwanul Siddique, lead author of a recent paper published in the journal Science Advances. Siddique’s paper uses these butterfly nanostructures as inspiration for a new type of solar cell design that can absorb more sunlight than traditional solar panels.
“A lot of insects have structural colors, where their colors come from nanostructures,” says Siddique. For instance, the bright blues and greens of many Morpho butterflies are caused by tiny tree-like shapes in the wings, less than a millimeter across. These nanostructures absorb and reflect different colors of light at different angles, so the butterfly appears to ‘shimmer’ and change colors in the air.
The common rose butterfly has a similar trick. Its velvety black wings get their color from tiny microscopic holes that trap and absorb light, giving the butterfly a blacker color than would be possible otherwise. And to an engineer like Siddique, who works with solar cells, a type of structure that absorbs more light is exactly what he needed.
Siddique and his colleagues examined the nanostructures of the common rose butterfly under a scanning electron microscope and attempted to recreate those structures with a solar cell. By adding tiny microscopic holes to the solar cell, Siddique’s team dramatically increased the solar cell’s efficiency.
So why does adding some tiny holes make a solar panel better? Mostly, it’s because those tiny holes greatly increase absorption at extreme angles. Most solar panels have to be pointed directly at the sun in order to generate the most amount of energy. When they’re angled off to the side, they’re much less efficient. Thanks to the tiny holes catching more angled light, Siddique’s solar cells are around three times as efficient at extreme angles.
That could be great news for homeowners with rooftop solar installations. Rooftop solar panels are often fixed, which means they only generate lots of power for a few hours per day. With Siddique’s design, their solar panels could produce more power at all daylight hours, which would translate to more power at more times.
And if you’re thinking that adding lots of tiny holes to solar panels can’t be cheap, the solution to that problem can be found in the common rose butterfly too. The butterfly makes the holes in its wings pretty cheaply, after all, and Siddique and his team borrowed the butterfly’s methods for their own research.
All the butterfly has to do to create its nanostructures is to combine some proteins together. Due to chemical interactions, those proteins automatically form into the right nanostructure. Siddique’s team created artificial versions of those proteins and applied them to solar cells, creating a cheap and scalable way to produce more efficient solar panels.
With any luck, a few years of development will be all it takes to start placing solar panels with Siddique’s design on rooftops around the world.