Thinnest Light Absorber on Record: New Tech for Cleaner Energy

Solar cells can absorb light, converting it into energy for our use. Yet these cells can be limited by their size and how efficiently they undergo this process. Now, Stanford scientists have created the thinnest and most efficient absorber of visible light on record, paving the way to better solar cells for cleaner energy.

How are these new, thin light absorbers made? The researchers created thin wafers dotted with trillions of round particles of gold. Each gold nanodot was about 14 nanometers tall and 17 nanometers wide. The wafers were created using a technique called block-copolymer lithography; each one contained about 520 billion nanodots per square inch. The scientists then fine-tuned the devices to absorb one type of light from one spot on the spectrum: reddish-orange light waves about 600 nanometers long.

"Much like a guitar string, which has a resonance frequency that changes when you tune it, metal particles have a resonance frequency that can be fine-tuned to absorb a particular wavelength of light," said Carl Hagglund, lead author of the study, in a news release. "We tuned the optical properties of our system to maximize the light absorption."

So how well did these wafers do? It turned out that they absorbed about 99 percent of the reddish-orange light. In addition, the researchers achieved a 93 percent absorption in the gold nanodots themselves. This meant that they had created a wafer that pushed the limits of what could be achieved for light harvesting.

While the scientists have created these wafers, though, they haven't yet had a chance to place them in actual solar cells. If they succeed, though, the scientists could create far more efficient cells that could lead to clear and more efficient energy.

"We are now looking at building structures using ultrathin semiconductor materials that can absorb sunlight," said Stacey Bent, one of the researchers, in a news release. "These prototypes will then be tested to see how efficiently we can achieve solar energy conversion."

The details of the new technology are published in the journal Nano Letters.