Polymer cores direct light from any source to solar cells – ScienceDaily


Rice University engineers have come up with a colorful solution for next generation energy collection: luminescent solar concentrators (LSCs) in your windows.

Led by Rafael Verduzco and postdoctoral researcher and lead author Yilin Li of Rice’s Brown School of Engineering, the team designed and built square “windows” that enclose a conjugated polymer between two clear acrylic sheets.

This thin middle layer is the secret sauce. It was developed to absorb light at a certain wavelength and guide it to the edges of panels lined with solar cells. Conjugated polymers are chemical compounds that can be tailored for a variety of applications with specific chemical or physical properties, e.g. B. conductive films or sensors for biomedical devices.

The polymer compound of the rice laboratory is called PNV (for poly[naphthalene-alt-vinylene]) and absorbs and emits red light, but by adjusting the molecular components it should be able to absorb light in a variety of colors. The trick is that as a waveguide it accepts light from any direction but restricts its exit and focuses it on the solar cells that convert it into electricity.

“The motivation for this research is to solve energy problems for buildings through integrated photovoltaics,” said Li, who started the project as part of a “Smart Glass” competition. “At the moment, solar roofs are the most common solution, but you have to point them toward the sun to maximize their efficiency, and their appearance is not very attractive.

“We thought, why can’t we make colorful, transparent, or translucent solar panels and put them outside of buildings?” he said.

The study appears in the journal Polymer International.

Admittedly, the amount of juice produced by the Rice team’s test units is far less than that collected by even the average commercial solar cells, which routinely convert around 20% of sunlight into electricity.

But LSC windows never stop working. They like to convert light from inside the building into electricity when the sun goes down. In fact, tests showed that they convert ambient light from LEDs more efficiently than direct sunlight, even though the sunlight was 100 times stronger.

“Even indoors, if you hold up a panel, you can see very strong photoluminescence at the edge,” demonstrated Li. The panels he tested showed an efficiency of power conversion of up to 2.9% in direct sunlight and 3.6% with LED ambient light.

According to Verduzco, different types of luminophores have been developed over the past decade, but rarely with conjugated polymers.

“Part of the problem with using conjugated polymers for this application is that they can be unstable and degrade quickly,” said Verduzco, professor of chemical and biomolecular engineering, and materials science and nanotechnology. “But we have learned a lot about improving the stability of conjugated polymers in recent years, and in the future we can design the polymers for both stability and the desired optical properties.”

The lab also simulated the energy return of panels up to 120 inches square. They reported that these panels would provide a little less energy but still add to a household’s needs.

Li noted that the polymer could also be tuned to convert energy from infrared and ultraviolet light so that these plates remain transparent.

“The polymers can even be printed in patterns in the plates so that they can be turned into works of art,” he said.

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