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Standard solar panels miss half of all sunlight but these tiny gold balls could finally fix the problem.
At any given moment, 89,000 terawatts of raw solar power is slamming into the Earth’s atmosphere. It is a mind-boggling amount of energy. But right now, our best technologies are essentially trying to catch a raging river with a leaky bucket.
Solar radiation arrives in a mix of different light wavelengths: about 3 to 5 percent is ultraviolet, 40 to 45 percent is visible light, and a massive 50 to 55 percent is infrared. Standard photovoltaic cells — the traditional solar panels you see on rooftops — do a decent job converting visible light and a tiny slice of the near-infrared spectrum into electricity. But they let the vast majority of that heat-rich infrared energy slip right by.
But for some scientists in Korea, this is not nearly enough.
Engineers have tried to capture this lost energy using massive mirror arrays and solar-thermal collectors. These systems absorb both visible and infrared light reasonably well to generate heat. However, their efficiency hits a wall because the surface coatings they rely on rarely achieve near-total absorption.
Even when scientists turn to highly engineered nanomaterials — like individual gold and silver nanoparticles — the results have been underwhelming. These nanoparticles primarily absorb only the visible wavelengths, leaving the vast, energy-rich infrared spectrum largely untouched.
If we want to decarbonize the planet and build a more efficient grid, we cannot afford to waste half the sun’s energy. We need a material that eats the entire spectrum.
Enter the “plasmonic supraball.”
A team of researchers at the KU-KIST Graduate School of Converging Science and Technology in Seoul, South Korea, has engineered a brilliant workaround.
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Instead of using scattered, individual gold nanoparticles, the researchers figured out how to make thousands of these particles self-assemble into microscopic clusters suspended in liquid. They call these micrometer-scale clusters “supraballs.”
Clustering these nanoparticles into a sphere fundamentally changes how the gold interacts with light. When sunlight hits these supraballs, the outer layer of gold nanoparticles traps the visible light and ultraviolet rays. Meanwhile, the dense core of the sphere acts like a trap for the longer, near-infrared waves. In physics terms, they are combining localized surface plasmon resonances on the outside with multipolar Mie-type magnetic resonances on the inside.
In simpler terms: it is a roach motel for photons. Light checks in, but it does not check out. The light bounces around inside the supraball until it transforms entirely into heat.
The performance metrics are genuinely staggering. Through computer simulations and real-world testing, the researchers proved that these supraball films can absorb around 89 to 90 percent of the wavelengths across the full solar spectrum. That is a massive leap compared to conventional gold nanoparticle films, which tap out at roughly 45 percent absorption.
To see if this translates to usable energy, the team tested their creation on a commercial thermoelectric generator (TEG) — a device that turns heat directly into electricity. They simply dropped a liquid solution full of these supraballs onto the generator and let it dry. As the liquid evaporated, it left behind a dense, dark film. When exposed to simulated sunlight, the supraball-coated generator ran much hotter, producing roughly 2.4 times the electrical power output of a generator coated with standard nanoparticles.
But power output is only half the story. The real game-changer here is how ridiculously easy this is to manufacture.
Historically, building hyper-efficient solar absorbers required expensive vacuum chambers, highly trained personnel, and pristine clean rooms. It is a bottleneck that keeps a lot of great tech locked in the lab.
The supraball liquid, on the other hand, can literally be dripped onto a surface and dried at room temperature. No intense heat or specialized vacuums are required. This means the coating can be applied cheaply to practically any existing thermal-based solar system, from commercial water heaters to advanced hybrid panels that harvest both light and heat.
“Our plasmonic supraballs offer a simple route to harvesting the full solar spectrum,” says researcher Seungwoo Lee. “Ultimately, this coating technology could significantly lower the barrier for high-efficiency solar-thermal and photothermal systems in real-world energy applications.”
This kind of plug-and-play upgrade is exactly what the renewable energy sector needs right now. We do not necessarily have to reinvent the grid overnight to make a massive impact. Sometimes, we just need a better bucket.
The findings appeared in the journal ACS Applied Materials & Interfaces.
Tibi is a science journalist and co-founder of ZME Science. He writes mainly about emerging tech, physics, climate, and space. In his spare time, Tibi likes to make weird music on his computer and groom felines. He has a B.Sc in mechanical engineering and an M.Sc in renewable energy systems.
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© 2007-2025 ZME Science – Not exactly rocket science. All Rights Reserved.
