To capture as much energy as possible from the Sun, we must improve the efficiency of solar cells. Currently, most technology only picks up visible light, which means the rest of the spectrum is wasted. Now, researchers at Lawrence Berkeley National Laboratory have developed a way to use nanoparticles coated with special organic dyes to take advantage of infrared light, which could allow solar cells to broaden the spectrum and be more efficient, is working to double their efficiency.
Particles called upconverting nanoparticles (UCNP) contain lanthanide metal ions such as ytterbium and erbiumYtterbium absorbs infrared light and reflects it back to erbium, which reflects it back as visible green light. It was later found that coating nanoparticles with an organic dye increased their efficiency. The problem was that they degraded quickly when exposed to light.
“The dyes appeared to degrade almost immediately after exposure to light, and no one knew exactly how the dyes interacted with the surface of the nanoparticles.Says Emory Chan, co-lead author of the study.
Now, scientists at the Berkeley Lab claim to have achieved a stable process to design systems that perform better. They found that the lanthanides in the particles cause the dyes to enter a state where they can merge several photons into a single photon of visible light, more efficiently transferring the energy of lanthanides. Acting as concentrators of light.
“Dyes act as solar concentrators at the molecular scale, channeling the energy of near infrared photons to nanoparticlesSays P. James Schuck, co-lead author of the study.
Observation of the light emission of the dye and the absorption of the UCNP showed that the peaks of the two measurements aligned, revealing the functioning of these nanoparticles.
Based on these findings, the researchers designed new UCNPs to make the process more efficient. After increasing the concentration of lanthanides in the particles from 22% to 52%, the team found that their new dyed UCNPs were 33,000 times brighter and 100 times more effective than they would be without the dye.
Unfortunately, the downside is that the dyes are still very unstable – for these experiments, the researchers had to store them in nitrogenous environments. They still have the challenge of developing protective coatings for UCNPs.
With those drawbacks resolved, the team says the particles could be used to make solar cells that can take more advantage of the light spectrum. Since they are transparent to visible light, a layer can be placed on top of normal solar cells.
“These organic dyes capture broad bands of near infrared light“Says Bruce Cohen, co-lead author of the study.”Since near infrared light wavelengths are often not used in solar technologies that focus on visible light, and these dye-sensitized nanoparticles efficiently convert near infrared light to visible light, they increase the possibility of capturing much of the solar spectrum that is otherwise wasted and integrating it into existing solar technologies“.
More information: Berkeley Laboratory