This seems interesting.

He [Stanford Ovshinsky, inventor of the nickel metal hydride (NiMH) technology used for building batteries] points out that by storing hydrogen reversibly in disordered solids, this solves the problems of storage, kinetics (speed of uptake and release) and cycle life. To this end, Ovshinsky and his colleagues have created a family of hydride compounds capable of real-world applications. Underpinning this is the vast catalytic surface area found in these materials, which means that when fabricated into thin film, continuous web, multi-junction devices, they can use the entire spectrum of sunlight to break up water to generate hydrogen, which is stored within the material ready for later use.

Instead of a solar cell which generates electricity it generates hydrogen, from water, and stores it internally. I wonder how long it takes to refuel itself after hydrogen depletion? That's not the only question that comes to mind.