These are very hopeful news, immersed as we are in the consequences of major oil and nuclear disasters, solar energy (as well as other renewables) are the way to go and there have been impressive advances, specially in the field of solar power, in the last years.
While the comparison is made to a leaf, nature's photosynthetic power plant, the device is more like a game card but thinner, and also requires a gallon (some 4.5 liters) of water and a fuel cell (for storage of hydrogen and oxygen). In bright sunlight this tiny device makes enough energy for a normal home to run the whole day... and night.
This leaf is, it seems, ten times more efficient that natural leaves.
Source: Science Daily
See also: Leherensuge (my old blog), label: solar energy, for other interesting advances in the field since 2008 (many of them from the MIT, which seems to be leading the research in this field, as is the case now).