Solar Energy Could Become More Efficient Thanks to Science

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Researchers in the US have found a new way to improve the amount of light being caught by solar panels.

The international science collective believes it can now design and function nanoparticles to catch light missed by solar cells and convert it to usable energy, according to their study published in Nature Photonics.

The tiny particles were coated with organic dyes to enhance their ability to catch near- infrared light and to reemit the light in the visible light spectrum.

The team, led by scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, were able to understand how the mechanism that enables the dyes on nanoparticles to function as antennas to gather a broad range of light

They then successfully re-engineered the nanoparticles to further amplify the particles’ light-converting properties.

Researchers found the dye itself amplifies the brightness of the reemitted light about 33,000-fold, and its interaction with the nanoparticles increases its efficiency in converting light by about 100 times.

“..They raise the possibility of capturing a good portion of the solar spectrum that otherwise goes to waste, and integrating it into existing solar technologies,” said Bruce Cohen, a scientist at Berkeley Lab’s Molecular Foundry who helped to lead the study along with Molecular Foundry scientists P. James Schuck (now at Columbia University), and Emory Chan. The Molecular Foundry is a nanoscience research centre.

The team had worked for nearly 10 years to study the upconverting nanoparticles (UCNPs) used in this study.

UCNPs absorb near-infrared light and efficiently convert it to visible light, an unusual property owing to combinations of lanthanide metal ions in the nanocrystals.

A 2012 study suggested that dyes on the UCNPs’ surface dramatically enhances the particles’ light-converting properties, but the mechanism remained a mystery.

“There was a lot of excitement and then a lot of confusion,” Cohen said. “It had us scratching our heads.”

Experiments led by David Garfield, a UC Berkeley Ph.D. student, and Nicholas Borys, a Molecular Foundry project scientist, showed a symbiotic effect between the dye and the lanthanide metals in the nanoparticles.

The proximity of the dyes to the lanthanides in the particles enhances the presence of a dye state known as a “triplet,” which then transfers its energy to the lanthanides more efficiently.

The triplet state allowed a more efficient conversion of multiple infrared units of light, known as photons, into single photons of visible light.

The studies showed that a match in the measurements of the dye’s light emission and the particles’ light absorption confirmed the presence of this triplet state, and helped inform the scientists about what was at work.