Researchers at the University of Cambridge have developed a new innovative lithium-ion battery that can be directly charged with sunlight. A mechanical engineer at the University, Michael De Volder, describes it as a solar panel and battery, for the price of only a battery.
The technology uses graphene oxide to aid electron transport, which increases its overall performance. The battery has potential uses part worldwide, most notably in areas with a less rigorous power grid or away from civilization altogether.
For more information about the batteries, see this article by Graphene Info.
Image from research paper: Light Rechargeable Lithium-Ion Batteries Using V2O5 Cathodes