Fabric solar cells turn any surface into a power source, MIT engineers say

Engineers at MIT said they developed ultralight fabric solar cells that can readily turn any surface into a power source.

The durable, flexible solar cells are thinner than a human hair, and may be glued to a strong, lightweight fabric, making them easy to install on a fixed surface. 

They can provide energy as a wearable power fabric or can be transported and deployed in remote locations to help in emergencies. 

The researchers said the cells are one-hundredth the weight of conventional solar panels, generate 18 times more power per kilogram, and are made from semiconducting inks using printing processes that may be scaled in the future to large-area manufacturing.

Researchers said the thin and lightweight solar cells can be laminated onto many different surfaces. For instance, they could be integrated onto the sails of a boat to provide power while at sea, adhered onto tents and tarps that are deployed in disaster recovery operations, or applied to the wings of drones to extend their flying range. 

Their research was published in Small Methods.

The research engineers said that traditional silicon solar cells are fragile, meaning they must be encased in glass and packaged in thick aluminum framing, which limits where and how they can be deployed.

Six years ago, the MIT research team produced solar cells using an emerging class of thin-film materials that were so lightweight they could sit on top of a soap bubble. One drawback was that these ultrathin solar cells were fabricated using complex, vacuum-based processes, which can be expensive and challenging to scale up.

In their most recent work, the researchers set out to develop thin-film solar cells that are entirely printable, using ink-based materials and scalable fabrication techniques.

To produce the solar cells, they used nanomaterials that are in the form of a printable electronic inks. Working in the MIT.nano clean room, they coated the solar cell structure using a slot-die coater, which deposits layers of the electronic materials onto a prepared, releasable substrate that is around 3 microns thick. Using screen printing (a technique similar to how designs are added to silkscreened T-shirts), an electrode was deposited on the structure to complete the solar module. 

The researchers then peeled off the printed module, which was about 15 microns thick, off the plastic substrate, forming an ultralight solar device.

They said that such thin, freestanding solar modules are challenging to handle and can easily tear, making them difficult to deploy. To address this, the MIT team searched for a lightweight, flexible, and high-strength substrate to which they could adhere the solar cells. They identified fabrics as the optimal solution, as they provide mechanical resilience and flexibility with little added weight.

One material was a composite fabric that weighs 13 grams per square meter and is commercially known as Dyneema. By adding a layer of UV-curable glue, the researchers adhered the solar modules to sheets of this fabric, forming . This forms an ultra-light and mechanically robust solar structure.

When they tested the device, the MIT researchers found it could generate 730 watts of power per kilogram when freestanding and about 370 watts-per-kilogram if deployed on the Dyneema fabric.

By comparison, they said a typical rooftop solar installation in Massachusetts is about 8,000 watts. To generate that same amount of power, the fabric photovoltaics would add about 20 kilograms (44 pounds) to the roof of a house.

They also tested the durability of their devices and found that, even after rolling and unrolling a fabric solar panel more than 500 times, the cells retained more than 90% of their initial power generation capabilities.

The researchers said their solar cells still would need to be encased in another material to protect them from the environment. The carbon-based organic material used to make the cells could be modified by interacting with moisture and oxygen in the air, which could deteriorate their performance.

The research was funded in part by the MIT Energy Initiative, the U.S. National Science Foundation, and the Natural Sciences and Engineering Research Council of Canada.