At MIT, researchers are developing flexible photovoltaic cells thinner than a hair

Transform any everyday surface into a source of solar energy. This is the goal set by a team of engineers from the prestigious Massachusetts Institute of Technology (MIT), which led to the development of ultra-light photovoltaic cells. Durable, flexible and thinner than a hair, these new types of cells are about 100 times lighter than a traditional solar collector, which allows them to generate 18 times more energy per kilo.

This is not their only advantage: they are made from semiconductor inks, which means that these cells can be manufactured on a very large scale via a process derived from printing. And because they are extremely thin and light, these solar cells can be laid on countless surfaces. The researchers thus imagine them installed on the wings of a drone, the sail of a boat, the canvas of a tent or the fabric of a garment.

“The parameters used to evaluate new solar cell technology are generally limited to their conversion efficiency and their cost in dollars per watt. Integrability — that is, the ease with which the new technology can be adapted — is yet equally important. Lightweight solar fabrics enable this integrability, which has provided the impetus for current work. We are working to accelerate the adoption of solar energy, given the current urgency to deploy new carbon-free energy sources”says Vladimir Bulović, director of MIT.nano and lead author of the comprehensive technical publication related to this work.

Solutions to improve cell resistance

Obviously, there is the question of the resistance of these solar cells. Indeed, we are used to seeing photovoltaic cells embedded in resistant structures with a view to their integration into roof panels. Here, the researchers ultimately used a lightweight, flexible and strong substrate in the form of fabrics (known as Dyneema), to affix their solar modules to, which are about 15 microns thick. “With very little extra weight, you get a flexible and tear-resistant solar material”comment the researchers.

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What is interesting is that the solar modules are printed on a plastic substrate for their manufacture, before being peeled off and reused on another material. An approach selected by the researchers to decouple the manufacture of solar cells from their end use, in order to open the way to a multitude of possible uses.

This is an evolution of initial work started six years ago by the ONE Lab (Organic and Nanostructured Electronics Laboratory), also directed by Vladimir Bulović. The latter had already enabled the creation of ultrathin solar cells, but relied on a much more complex and expensive manufacturing process. These cells were also much more fragile and delicate to handle.

20 kilos for 8000 watts of electrical production

MIT researchers were able to test these cells in real conditions and found that they can provide 730 watts of energy per kilo (370 watts when integrated with Dyneema fabrics). “A typical rooftop solar installation in Massachusetts is about 8000 watts. To produce the same amount of energy, our fabric photovoltaic panels would only add about 20 kilograms to the roof of a house.“, they indicate.

It is, indeed, much lighter than the installation of traditional photovoltaic panels, which for this capacity weigh about 400 kilos. As for the durability of the material, according to their tests, the cells on tissue lose only 10% of their capacity to transform into energy after 500 “bends”.

Still works before a possible commercialization

Next step ? The creation of sufficient but very light, very fine protection, for uses requiring greater resistance. The idea being, here too, to protect the solar cells from humidity and oxygen in the air, to maximize their performance over time, knowing that alterable organic materials are involved in the manufacturing process.

“We strive to eliminate as many non-solar materials as possible while maintaining the form factor and performance of these ultralight and flexible solar structures. For example, we know that the manufacturing process can be simplified by printing the detachable substrates , as we do for the other layers of our device. This would accelerate the time to market of this technology”they conclude.

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