This is cool:
A practical solar energy system usually includes solar cells that convert light to electricity and batteries that store the energy for later use.
Scientists from Toin University of Yokohama in Japan have designed a single, compact device that can both convert solar energy to electricity and store the electricity. "We succeeded in incorporating both photovoltaic and storage functions in a single cell with a thin, sandwich-type structure," said Tsutomu Miyasaka, a researcher at the University.
The researchers' photocapacitor is also efficient at capturing energy from weak light sources like sunlight on cloudy or rainy days and indoor lighting.
The light-driven, self-charging capacitor could eventually be used to power portable electronic devices like phones, cameras, and PDAs, said Miyasaka. "Users can just bring the device anywhere and expose it to indoor and outdoor ambient light whether they need power or not [then] release the stored electricity anytime they want," he said.
thanks to taylor for pointing this out to me ...