Silicon p-i-n junction optical fibers could lead to photovoltaic fabrics

University Park, PA and Southampton, England--Researchers at Pennsylvania State University and the University of Southampton have created a silicon-based optical fiber with solar-cell capabilities that is scalable to many meters in length and has a bend radius of about 400 microns. Possible in the future: weaving together solar-cell silicon wires to create flexible, curved, or twisted solar fabrics. The findings are posted in an early online edition of Advanced Materials and will be published on a future date in the journal's print edition.

The team's new findings build on earlier work addressing the challenge of merging optical fibers with silicon chips. Rather than merge a flat chip with a round optical fiber, the team found a way to build a new kind of optical fiber with its own integrated electronic component, bypassing the need to integrate fiber-optics with chip-based electronics. To do this, they used high-pressure chemical vapor deposition to deposit semiconducting materials directly into holes in optical fibers.

In their new research, the team members have used the same high-pressure chemistry techniques to make a fiber out of crystalline silicon that can function as a photovoltaic cell. "Our goal is to extend high-performance electronic and solar-cell function to longer lengths and to more flexible forms. We already have made meters-long fibers but, in principle, our team's new method could be used to create bendable silicon solar-cell fibers of over 10 meters in length," says John Badding, a professor of chemistry at Penn State University. "Long, fiber-based solar cells give us the potential to do something we couldn't really do before: We can take the silicon fibers and weave them together into a fabric with a wide range of applications such as power generation, battery charging, chemical sensing, and biomedical devices."

The military especially is interested in designing wearable power sources for soldiers in the field, Badding notes.

"Another intriguing property of these silicon-fiber devices is that as they are so compact, they can have a very fast response to visible laser light," says Pier J. A. Sazio of the University of Southampton. "In fact, we fabricated fiber-based photodetectors with a bandwidth of over 1.8 GHz."