They spend all day baking in the sun, but that doesn't mean solar panels capture all the light that hits them. Generally speaking, solar cells are capable of harnessing visible light for energy generation, while other parts of the electromagnetic spectrum go by unnoticed, including infrared. Much work is being done to bring others into the mix, including at Sweden's KTH Royal Institute of Technology where scientists have developed a new film they say can be layered over the top of solar cells to boost their efficiency by as much as 25 percent.
One of the ways scientists have looked to increase the performance of solar panels is by supercharging them with special kinds of nanoparticles. By doping these tiny particles with dyes containing metal ions such as lanthanide, it is possible to equip them with the ability to make use of other types of light (such as infrared) and then have it converted into energy.
These are known as upconverting nanoparticles (UCNPs), and they form the basis of the breakthrough at KTH Royal Institute of Technology. The team says there is currently room for improvement with this kind of tech, writing that because UCNPs have an excitation threshold that is "much higher" than what the infrared light can offer them, a lot of its energy continues to go to waste.
The team's solution was to develop a polymer-based array, made of nanocrystals mixed with a series of microlenses, to shape the way the light comes in and boost the performance of the UCNPs.
“The ability of the microlenses to concentrate light allows the nanoparticles to convert the weak infrared light radiation to visible light useful for solar cells,” says Hans Ågren, professor in theoretical chemistry and leader of the research team.
Applied as a thin film over the top of a regular solar cell, this has the effect of spatially modulating the infrared light, concentrating it in just the right way to greatly improve the efficiency of the energy conversion.
“We have achieved a 10 percent increase in efficiency without yet optimizing the technology,” Ågren says. “With a little more work, we estimate that a 20 to 25 percent increase in efficiency could be achieved.”
In the meantime, the team has patented the technology and published its research in the journal Nanoscale.
