We couldn’t be happier that solar energy is becoming cheap and accessible to all kinds of people and businesses. You might have noticed some of your neighbors installing rooftop solar panels, or you might be a user yourself. But you likely noticed that they also look kinda dull. Solar panels come in two basic and, frankly speaking, monotonous colors: black and blue.
Wait, I hear you, and I’m on your side. Here we are getting clean energy from the sun and at a low cost to boot (solar is cheaper than the grid in many places in the U.S., by the way), but we’re complaining because we’re tired of seeing too much blue in our neighborhoods. Trust me, as a kid growing up in Eastern Europe, there are worse eye sores one could have in their local neighborhood — such as living next door to a decaying coal-fired power plant.
But that’s just how humans are. They’re never really content, and that’s not such a bad thing all the time. It means we find solutions and build diversity.
In a new study, researchers in China have finally created solar panels that come in different colorful hues that are nearly as efficient as traditional ones.
Solar panels are blue because they’re made from polycrystalline silicon, which is why they’re also known as polycrystalline solar panels. They also have an anti-reflective coating that helps improve their energy absorbing capacity and efficiency. Black solar panels are made from highly pure monocrystalline silicon, which helps absorb almost all the wavelengths of light, thereby appearing black. Black solar cells are thus generally more efficient than blue cells. If you ever wore a black shirt on a hot summer’s day, then you’ve felt this effect.
If you paint over a black or blue solar cell, the paint will naturally block some of the sunlight and hinder power output. So the team of researchers at Jiao Tong University and Xinjiang University went a totally different route that doesn’t involve changing the amount of absorbed energy, taking inspiration from nature to develop structural colors.
The beautiful metallic blue of butterfly wings, for instance, is not produced by pigments but rather stems from microscopic and nanoscopic structures present on the appendages. These lattice structures scatter light and only reflect back to our eyes a very narrow, selective portion of light.
The Chinese researchers aren’t the first to come up with this idea, but previous efforts resulted in solar panels that were iridescent or very expensive. Their solution was to spray a very thin layer of photonic glass — a disordered arrangement of microscopic zinc sulfide spheres — which let most of the light pass right through it but reflects certain selective wavelengths. By tweaking these wavelengths, the researchers could essentially alter the color of the solar panel.
Using this approach, the authors made solar panels with blue, green, and purple hues with less than a 1% drop in overall efficiency. The photonic glass proved durable during tests and the technology is supposed to be scalable for mass manufacturing.
“These results confirm photonic glass as a promising strategy for colored PVs possessing high efficiency and practical applicability,” the authors wrote in their study.
The findings appeared in the journal ACS Nano.