Gold nanoparticles boost solar cell efficiency by capturing full sunlight spectrum

Though the sun produces more energy than we would ever need on Earth, current solar harvesting technologies are limited, and they don’t capture as much sunlight as they could.

Now, a team of scientists is looking to level up our ability to harvest sunlight using innovative technologies.

The team from Korea University claims it has discovered a new material that absorbs nearly every wavelength in the solar spectrum. Crucially, their gold nanospheres, named supraballs, absorb some wavelengths that traditional photovoltaic materials miss.

Harvesting the full solar spectrum

In tests, the scientists applied a layer of supraballs onto a readily available off-the-shelf electricity converter. By simulating sunlight, they demonstrated that the material almost doubled solar energy absorption when compared with traditional materials.

The team is one of many investigating materials that absorb light across the solar spectrum. The higher the range of absorption, the better the material is at harvesting solar energy.

Gold and silver nanoparticles (NPs) have great potential because they are easy to manufacture and relatively inexpensive. However, existing NPs are only able to absorb visible wavelengths, meaning they only cover a fraction of the full solar spectrum.

To broaden the range of wavelengths NPs can absorb, the team proposed using self-assembling gold supraballs. These are gold NPs that clump together and form tiny spheres. The scientists, Jaewon Lee, Seungwoo Lee, and Kyung Hun Rho adjusted the diameter of the supraballs to maximize the absorption of wavelengths present in sunlight.

“Our plasmonic supraballs offer a simple route to harvesting the full solar spectrum,” Seungwoo Lee explained in a press statement. “Ultimately, this coating technology could significantly lower the barrier for high-efficiency solar-thermal and photothermal systems in real-world energy applications.”

Investigating supraballs

To determine the efficiency of the supraballs, the team used computer simulations. This helped them optimize the design of individual supraballs and predict their overall performance.

Their initial results showed that supraballs should absorb more than 90 percent of wavelengths from sunlight.

To validate their findings, they turned to real-world tests. The scientists dried a liquid solution containing the supraball structures on the surface of a commercially available thermoelectric generator (TEG)—a device used to convert light into electricity.

The scientists were able to create this film of gold supraballs under ambient room conditions, without needing a clean room or specialized equipment to generate extreme temperatures.

The team then used an LED solar simulator to test the supraball-coated TEG. In their demonstrations, the TEG showed an average solar absorption of roughly 89 percent. According to the scientists, this is almost double the 45 percent rate of a TEG using a conventional film made from single gold NPs.

The study was published in the journal ACS Applied Materials & Interfaces.