Imagine a photovoltaic cell or module that actually produces and stores energy, acting as a battery and producing power even after dark. New research into silicon-based supercapacitors at Vanderbilt University shows that it’s possible. 
Supercapacitors have long been looked at as a potential alternative to batteries for energy storage, but they remain bulky and expensive with low storage density. However, they offer some significant advantages over conventional batteries. For instance, they can charge and discharge energy rapidly. They also promise lighter weight and much longer lifespans than batteries do because of the way supercapacitors store energy. 
Whereas a battery stores energy in a chemical reaction, supercapacitors store energy in ions on the surface of a porous material — usually activated carbon, Vanderbilt explains. So, as their energy density capacity increases, they become more attractive. Graphene and nanostructuring with silicon may prove the panacea for such devices. 
Researchers at the university published their findings in the Oct. 22 issue of the journal Scientific Reports. They propose making a supercapacitor out of silicon — a first — and that such devices can be built into a silicon chip along with the microelectronic circuitry that it powers. “It should be possible to construct these power cells out of the excess silicon that exists in the current generation of solar cells, sensors, mobile phones and a variety of other electromechanical devices, providing a considerable cost savings,” the university says.
“If you ask experts about making a supercapacitor out of silicon, they will tell you it is a crazy idea,” says Cary Pint, the assistant professor of mechanical engineering who headed the development. “But we’ve found an easy way to do it,” he added.