At any given moment, the Earth is bathed in an astonishing 89,000 terawatts of solar energy. Yet despite decades of progress in solar technology, most systems still fail to capture the full spectrum of sunlight—leaving vast amounts of potential power untapped. Researchers at the KU-KIST Graduate School of Converging Science and Technology in Seoul have now unveiled a breakthrough that could change this equation: plasmonic colloidal “supraballs” made from gold nanoparticles that absorb nearly 90% of the solar spectrum.

A Simple Coating That Could Transform Solar Forever


Solar radiation spans ultraviolet, visible, and infrared wavelengths, but conventional photovoltaic cells only convert a portion of visible and near-infrared light into electricity. Other systems, such as concentrated solar power and solar-thermal collectors, broaden the range but remain limited by imperfect absorber materials and costly infrastructure. The new supraball technology offers a simpler, more efficient alternative.  

The process begins with a colloidal suspension of gold nanoparticles that self-assemble into micrometer-scale spheres. When deposited onto ceramic surfaces, these spheres form dense, textured films that trap photons across ultraviolet, visible, and near-infrared wavelengths. This trapping effect is driven by localized surface plasmon resonances at the nanoparticle surfaces and Mie-type resonances within the spheres. The result is a remarkable ~90% absorption rate across the solar spectrum, converting light into heat with far greater efficiency than conventional coatings. In fact, the supraballs generate nearly 2.4 times the power output of existing nanoparticle films.

Beyond their performance, the supraballs are notable for their practicality. They can be fabricated through low-complexity solution processing, applied directly to existing devices, and remain stable under long-term thermal exposure. This makes them particularly well-suited for thermal-based solar systems such as thermoelectric generators, solar-thermal collectors, and passive heating applications. They may also play a role in hybrid PV-thermal systems, where visible light is converted to electricity while the remaining spectrum is harvested as heat.

“Our plasmonic supraballs offer a simple route to harvesting the full solar spectrum,” explains 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.”

By combining cutting-edge nanotechnology with scalable manufacturing, this innovation points toward a future where solar energy systems can capture far more of the sun’s abundant power—bringing us closer to truly sustainable energy solutions.


Sources  
- Original article: New Atlas 
- Research publication: ACS Applied Materials & Interfaces (DOI: 10.1021/acsami.5c23149)