When the jacket supplies solar power

Luminous material

The newly developed solar collector is so flexible that it can be bent with tweezers. (Image: Empa)

Clothes instead of a socket: in the future, our clothes could help charge smartphones or laptops. A team of researchers has developed a material with special phosphors that can also use diffuse light to generate solar power and can be applied to textiles. This opens up numerous possibilities for producing energy directly where it is needed – for example for using everyday electronics.

Whether cell phone, smartwatch or notebook: The trend is towards mobile electronics. In our everyday life we ​​use more and more technical devices that are small and accompany us everywhere. Up to now, rechargeable batteries and batteries have usually provided the necessary electricity. But these are neither environmentally friendly nor particularly sustainable. In the course of the switch to renewable energy, scientists are therefore looking for solutions to also supply mobile devices with electricity, for example from solar energy.

Phosphors catch diffuse light

In the solar industry there are already the first materials that are supposed to facilitate the generation of energy from light and make it more efficient by making use of diffuse ambient light. These materials contain special phosphors and are called “Luminescent Solar Concentrators” (LSC). The phosphors in the LSC capture indirect light rays – i.e. diffuse light – and pass them on to the actual solar cell, which then converts the light into electrical energy. So far, however, these LSC have only been available as rigid components and are unsuitable for a wide range of uses – such as on textiles – because they are neither flexible nor water-resistant or permeable to air and water vapor.

A research team led by Chieh-Szu Huang from the Eidgenössische Materialprüfungs- und Forschungsanstalt (Empa) in Switzerland has now looked for a way to modify the carrier materials for these phosphors so that the solar contractors can be used in a more versatile way in the future. As a basis for their new material, the scientists therefore looked for a polymer that is flexible and air-permeable. Such a material, which has long been known in research, is made up of so-called “amphiphilic polymer connetworks” (APCN), which are already available in the form of silicone hydrogel contact lenses. The special properties of the polymer, the permeability for air and water vapor as well as the flexibility and stability, are not only advantageous for use in the human eye.

Solar collector to wear

To manufacture their new solar contractor, the research team mixed two different phosphors into the gel tissue of this polymer, which the scientists had previously examined for their potential for generating energy. “What is important for choosing this polymer is the fact that we can incorporate two immiscible phosphors on a nanometer scale and that they can interact,” says Huang’s colleague Luciano Boesel, explaining the procedure. “There are also other polymers into which these phosphors could be integrated, but they would clump together and the production of energy would no longer be possible.” The researchers then checked the behavior and the optimal dosage of the two phosphors in several Test runs.

And indeed: with the addition of a certain concentration of the luminescent substances, the researchers obtained a flexible and effective solar collector. Just like on large collectors, the phosphors in the gel can capture a much wider spectrum of light rays than is possible with conventional photovoltaics, say Huang and his colleagues. At the same time, however, the novel polymer material can be applied to textile fibers, for example, without it becoming brittle and prone to cracks or without water vapor accumulating in the form of sweat inside the coated garment.

According to the researchers, such body-worn solar collectors offer enormous benefits for the ever-increasing demand for energy for portable devices. Instead of sockets, electricity could come directly from your own clothing in the future. Thanks to the new material, jackets, t-shirts and the like are turned into solar collectors and could thus function as a mobile energy supplier, according to the scientists.

Source: Federal Materials Testing and Research Institute, specialist article: Nano Energy, doi: 10.1016 / j.nanoen.2020.105039

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