The first flexible, fiber-optic solar cell that can be woven into clothes
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An international team of engineers, physicists, and chemists have created the first fiber-optic solar cell. These fibers are thinner than human hair, flexible, and yet they produce electricity, just like a normal solar cell. The US military is already interested in weaving these threads into clothing, to provide a wearable power source for soldiers.
In essence, the research team started with optical fibers made from glass — and then, using high-pressure chemical vapor deposition, injected n-, i-, and p-type silicon into the fiber, turning it into a solar cell. Functionally, these silicon-doped fiber-optic threads are identical to conventional solar cells, generating electricity from the photovoltaic effect. Whereas almost every solar cell on the market is crafted out of 2D, planar amorphous silicon on a rigid/brittle glass substrate, though, these fiber-optic solar cells have a 3D cross-section and retain the glass fiber’s intrinsic flexibility.
The lead researcher, John Badding of Penn State University, says the team has already produced “meters-long fiber,” and that their new technique could be used to create “bendable silicon solar-cell fibers of over 10 meters in length.” From there, it’s simply a matter of weaving the thread into a fabric. Badding says that the military is “interested in designing wearable power sources for soldiers in the field,” but unfortunately he falls short of actually demonstrating some woven fabric. As we can see in the picture above, the solar cell fiber certainly looks flexible — but we’ll have to take Badding’s word for it that it can turn right angles, and withstand everyday garment stresses, without shattering.
Moving forward, the potential for flexible, woven solar cells is enormous. On the most basic, immediate level, you can imagine a baseball cap or t-shirt that can recharge your smartphone. As we move towards bionic implants and other biomedical devices, though, there is a very pressing need to develop a wearable power source — and fiber-optic solar cells could certainly be it.
These fibers also have two other intriguing properties that still need to be investigated. Due to their three-dimensional cross-section, they can absorb sunlight from any direction — unlike their conventional, 2D siblings that lose much of their efficiency when the sun sinks below a certain angle. Further, according to Pier Sazio, another member of the research team, they used the same silicon injection method to embed photodetectors inside the fiber. Sazio doesn’t extrapolate on what this might lead to, but it’s fun to speculate: A wearable computer with built-in solar charging and high-speed networking? Neat.
Research paper: DOI: 10.1002/adma.201203879 – “Silicon p-i-n Junction Fibers”