MIT researchers have demonstrated the thinnest, lightest solar cells that have ever been produced. The solar cells are so thin that 50 of them would fit inside the width of a human hair. To show off their invention, the researchers placed their solar cells on a bubble, which didn’t pop under the insubstantial weight. This new solar cell could be especially useful for applications where it is important to maximize the power to weight ratio, such as on a spacecraft, or perhaps on Google’s internet balloons. The current version is made from thin plastic, but the researchers say it can also be placed on paper or fabric, so it could be used for solar-powered wearable devices.
The secret to their success is an all-in-one approach, where the solar cell, its substrate, and a protective coating are all grown together. After years of trial and error, the researchers perfected their technique: a straight-forward process that—unlike conventional solar cells—doesn’t require high temperatures or harsh chemicals. “We put our carrier in a vacuum system, then we deposit everything else on top of it, and then peel the whole thing off,” explains research scientist Annie Wang.
Both the substrate and protective coating were made from parylene, a plastic coating that is commonly used to protect implanted biomedical devices and printed circuit boards from environmental damage. An organic material called DBP was sandwiched in the middle of parylene layers to absorb light. The researchers focused more on the technique than materials, but future versions of the ultra-thin solar cells could use quantum dots or perovskites, which could lead to better performance.
The innovative step is the realization that you can grow the substrate at the same time as you grow the device.
Now that they can check off the proof-of-concept stage of their project, the MIT team says that several years of additional research is needed before the solar cells can be commercialized. The process is described in a paper by Wang, Bulović, and MIT doctoral student Joel Jean, in the journal Organic Electronics.