There is little in the way of hard information at this point. The Japanese newspaper Nikkei disclosed the development, saying that the car would have solar cells, and that it would also be charged by solar cells on homes. Also according to Nikkei, the solar cells on the car will be as powerful as those on the house, capable of generating 2-5 kilowatts.
Toyota has talked publicly about a solar panel option on the next Prius, but that was called "a symbolic gesture" by an insider. Privateers have also done their part contributing to the idea of a Prius augmented by solar power, largely with mixed results. Nevertheless, Toyota has a keen partner in the venture: Panasonic. The giant consumer electronics maker that makes Prius batteries is in the midst of buying Sanyo, the world's 7th-largest solar cell maker. Nevertheless, solar cell technology isn't advanced enough to create a mass-market solar car, which is why reports claim it will be years before such a vehicle is on the market. As one Japanese solar energy expert said, "Even if you laid solar panels out on the entire roof of a house, you only generate enough energy to run two hairdryers." Hat-tip: Jarrett