MIT team makes solar cells as light and thin as soap bubbles

Researchers at the Massachusetts Institute of Technology (MIT) have developed the thinnest and lightest solar cells ever made, which could eventually be used to power the next generation of personal electronics.

The process of creating the small, flexible cells – measured at a thickness of only 1.3 micrometers and a surface density of 3.6 grams per square meter – was described by MIT professor and associate innovation dean Vladimir Bulović along with researcher Annie Wang and doctoral student Joel Jean in the April edition of Organic Electronics.

The scientists developed the organic cells by growing a parylene-C polymer substrate film in a vacuum, creating solar units that are comparable in their energy output to those utilizing a traditional glass design. By growing the cell, substrate, and coating together in a lab in one process, development was streamlined and the cells end up being less exposed than if the components were created separately.

“The innovative step is the realization that you can grow the substrate at the same time as you grow the device,” Prof. Bulović said in a MIT news release. The process can also be completed at room temperature without the addition of solvents and chemicals not used in the final product, unlike more demanding solar-cell production methods commonly employed today. Instead, the cell components are grown in a vacuum at room temperature simply through the vapor deposition of polymer precursors that eventually react and settle to form the cell’s parts together.

“It’s a very versatile and widely used manufacturing process,” MIT associate professor John Hart said of the vapor system, calling it “a very general process that can be tailored to many different applications,” including the formation of the solar cells.

So far, the researchers say the development of the cells is a proof-of-concept, and different materials could be used in the future if this method of manufacturing becomes more common. Still, the cells created so far are functional and efficient; they have a weight-based power of more than 6 watts per gram, about 400 times higher than the output of glass solar cells, despite being about 1/1000th the thickness of those units.

“If you breathe too hard, you might blow [them] away,” Mr. Jean said.

In order to collect the creations, the team used glass to carry the final cell systems, but the relatively simple process allows for the possibility of placing the cells on a variety of materials, including fabric, rubber, and more.

“It could be so light that you don't even know it's there, on your shirt or on your notebook,” Mr. Bulović said in a news release. “These cells could simply be an add-on to existing structures.”

While the team’s work so far using the vapor and polymer process has been successful, translating it from the lab to commercial production will take time but could open new options for the use of solar power. And Bulović is confident his group’s method will eventually be put out on a wider scale and made available to commercial products.

“How many miracles does it take to make it scalable?” he said. “We think it’s a lot of hard work ahead, but likely no miracles needed.”