Paper-thin solar panel: it can turn any surface into an energy source.
Researchers have developed a technique for producing ultra-thin, lightweight solar cells that can turn any surface into an energy source.
MIT engineers developed solar cells to be durable and flexible, and much thinner than human hair. They are glued to a strong, lightweight fabric, making them easy to install on a fixed surface. They can provide energy by wearing them or by being transported and rapidly deployed to remote locations for emergency assistance. They weigh one-hundredth that of conventional solar panels, generate 18 times more energy per kilogram, and are made with semiconductor inks using printing processes that could be scaled up to full-scale production in the future.
Being so thin and light, these solar cells can be laminated onto many different surfaces. For example, they could be integrated into the sails of a boat to provide power at sea, attached to tents and tarps used in disaster recovery operations, or attached to the wings of drones to extend their range.
“The metrics used to evaluate a new solar cell technology are typically limited to energy conversion efficiency and dollar cost per watt. Equally important is integrability, i.e. the ease with which new technology can be adapted. Lightweight solar fabrics enable integrability, boosting work,” says Vladimir Bulović, holder of the Fariborz Maseeh Chair in Emerging Technologies, leader of the Laboratory of Organic and Nanostructured Electronics (ONE Lab) and author of the paper describing the work.
The slimmed-down solar panel
Traditional silicon solar cells are fragile, so they must be encased in glass and packed in heavy, thick aluminum frames, which limits where and how they can be used.
Six years ago, the ONE Lab team produced solar cells using an emerging class of thin-film materials that are so light they can fit on top of a soap bubble . But these ultra-thin solar cells were being manufactured with complex, vacuum-based processes that can be expensive and difficult to scale. In this work, researchers set out to develop fully printable thin-film solar cells using ink-based materials and scalable fabrication techniques.
To produce the solar cells, they use nanomaterials in the form of printable electronic inks. They then coated the solar cell structure using a slit-coating machine, which deposits layers of electronic materials onto a prepared, removable substrate (just 3 microns thick). Using screen printing (a technique similar to adding designs to T-shirts), an electrode is deposited on the structure to complete the solar module.
It bends but does not break
Such thin, self-contained solar modules are difficult to handle and can break easily, making them difficult to use. To solve this challenge, the MIT team looked for a lightweight, flexible , high-strength substrate for solar cells to adhere to. The optimal solution has been identified in a composite fabric that weighs only 13 grams per square meter, known commercially as Dyneema. This fabric is made of fibers so strong that they were used as ropes to lift the sunken cruise ship, the famous Costa Concordia, from the bottom of the Mediterranean. By adding a layer of UV-curable glue, a few microns thick, the solar modules are adhered to Dyneema sheets. In this way an ultra- lightweight and mechanically robust solar structure is obtained .
“While it might seem simpler to print solar cells directly onto fabric, this would limit the choice of possible fabrics or other receiving surfaces to those that are chemically and thermally compatible with all the processing steps needed to make the devices. explains Saravanapavanantham.
When they tested the device, the MIT researchers found that it was capable of generating 730 watts of power per kilogram without Dyneema fabric and 370 watts per kilogram when used on high-strength Dyneema fabric, about 18 times that power per kilogram. to that of conventional solar cells. The researchers also tested the durability of their devices and found that even after rolling and unrolling more than 500 times, the cells retained more than 90% of their initial capacity to generate energy.
While being very light and flexible, these solar cells need to be coated with another material to protect them from the environment. “Embedding these solar cells in heavy glass, as is usually the case with traditional silicon solar cells, would minimize the value of the current advance, so the team is currently developing ultra -thin packaging solutions ,” Mwaura explains. “This would accelerate the transition of this technology to the market,” she adds.
