The lightweight fabric solar cells that MIT engineers have created can swiftly and simply convert any surface into a power source.
These resilient, flexible solar cells are attached to a sturdy, lightweight fabric and are much thinner than human hair, making them simple to mount on a permanent surface. They can be transported and quickly deployed in remote regions to provide assistance in an emergency or they can provide energy on the fly as a wearable power fabric. They are created of semiconducting inks utilizing printing techniques that can be scaled up in the future to large-area manufacturing and generate 18 times more power per kilogram than conventional solar panels.
These solar cells may be bonded onto many different surfaces because they are so light and thin. For example, they could be affixed to tents and tarps that are used in disaster recovery operations, integrated onto a boat’s sails to give power while at sea, or used on drone wings to increase their flying distance. This portable solar technology requires the little installation and is simple to integrate into constructed surroundings.
“The metrics used to evaluate a new solar cell technology are typically limited to their power conversion efficiency and their cost in dollars-per-watt. Just as important is integrability the ease with which the new technology can be adapted. The lightweight solar fabrics enable integrability, providing impetus for the current work. We strive to accelerate solar adoption, given the present urgent need to deploy new carbon-free sources of energy,” says Vladimir Bulović, the Fariborz Maseeh Chair in Emerging Technology, leader of the Organic and Nanostructured Electronics Laboratory (ONE Lab), director of MIT.nano, and senior author of a new paper describing the work.
Joining Bulović on the paper are co-lead authors Mayuran Saravanapavanantham, an electrical engineering and computer science graduate student at MIT; and Jeremiah Mwaura, a research scientist in the MIT Research Laboratory of Electronics. The research is published today in Small Methods.
Slimmed down solar
Conventional silicon solar cells must be wrapped in heavy, thick aluminum framing because they are fragile, which restricts where and how they may be used.
While it might appear simpler to just print the solar cells directly on the fabric, this would limit the selection of possible fabrics or other receiving surfaces to the ones that are chemically and thermally compatible with all the processing steps needed to make the devices. Our approach decouples the solar cell manufacturing from its final integration.
Mayuran Saravanapavanantham
A new class of thin-film materials that were so light they could sit on top of a soap bubble were used by the ONE Lab team six years ago to create solar cells. Nevertheless, to create these incredibly thin solar cells, complicated vacuum-based techniques were used, which can be expensive and difficult to scale up.
The goal of this effort was to create completely printable thin-film solar cells using ink-based materials and scalable production methods.
Nanomaterials in the form of printable electronic inks are used to make solar cells. Working in the MIT.nano clean room, they coat the solar cell structure using a slot-die coater, which deposits layers of the electronic materials onto a prepared, releasable substrate that is only 3 microns thick.
Using screen printing (a technique similar to how designs are added to silkscreened T-shirts), an electrode is deposited on the structure to complete the solar module. The printed module, which is roughly 15 microns thick, may then be peeled away from the plastic substrate to create an ultralight solar device.
Nevertheless, such tiny, freestanding solar modules are difficult to deploy since they are readily torn and difficult to manage. The MIT team looked for a thin, flexible, and strong substrate to which they could attach the solar cells in order to overcome this difficulty.
Fabrics were chosen as the best option since they offer mechanical resilience and flexibility with minimum additional weight. They found an ideal material a composite fabric that weighs only 13 grams per square meter, commercially known as Dyneema.
The fibers used to make this fabric are so powerful that they were used as ropes to raise the Costa Concordia from the bottom of the Mediterranean Sea. They affix the solar modules to sheets of this cloth by putting a thin coating of UV-curable glue on top of it. This forms an ultra-light and mechanically robust solar structure.
“While it might appear simpler to just print the solar cells directly on the fabric, this would limit the selection of possible fabrics or other receiving surfaces to the ones that are chemically and thermally compatible with all the processing steps needed to make the devices. Our approach decouples the solar cell manufacturing from its final integration,” Saravanapavanantham explains.
Outshining conventional solar cells
The gadget could produce 730 watts of power per kilogram when it was freestanding and roughly 370 watts per kilogram when it was mounted on the high-strength Dyneema fabric. This is nearly 18 times more power per kilogram than traditional solar cells.
“A typical rooftop solar installation in Massachusetts is about 8,000 watts. To generate that same amount of power, our fabric photovoltaics would only add about 20 kilograms (44 pounds) to the roof of a house,” he says.
Also, they put their products through a durability test and discovered that even after rolling and unrolling a fabric solar panel more than 500 times, the cells still maintained more than 90% of their original power-generating capacities.
Although though their solar cells are significantly lighter and more flexible than conventional cells, they would still require an additional substance to shield them from the elements. The cells’ performance could be negatively impacted by interactions between the carbon-based organic material used to create them and oxygen and moisture in the surrounding environment.
“Encasing these solar cells in heavy glass, as is standard with the traditional silicon solar cells, would minimize the value of the present advancement, so the team is currently developing ultrathin packaging solutions that would only fractionally increase the weight of the present ultralight devices,” says Mwaura.
“We are working to remove as much of the non-solar-active material as possible while still retaining the form factor and performance of these ultralight and flexible solar structures. For example, we know the manufacturing process can be further streamlined by printing the releasable substrates, equivalent to the process we use to fabricate the other layers in our device. This would accelerate the translation of this technology to the market,” he adds.
The MIT Energy Initiative, the U.S. National Science Foundation, and the Natural Sciences and Engineering Research Council of Canada fund this research, in part.
