When spacecraft go to Jupiter and farther, the sun's energy flux (energy per square meter per second) gets very weak and they would need very large solar cells.

For a while, the DAWN mission was the farthest mission to use solar cells. It hays very large solar panels ( see http://dawn.jpl.nasa.gov ). DAWN orbited one asteroid, Vesta, and is now heading to explore another asteroid, Ceres (which is now classified as a "dwarf planet").

More distant missions (Voyager, Cassini, New Horizons) use radioactive thermoelectric generators (RTG's).

However, one mission is on its way to Jupiter now, and it does have solar cells - JUNO.

http://www.nasa.gov/missi...ex.html#.VE6ubkuGnhM

It has now passed DAWN as the farthest spacecraft to use solar cells. Even though it has traveled more than 10 AU, it has still not reached Jupiter yet, which is 5.2 AU from the Sun.

You can see where all the missions are by downloading the "Eyes on the Solar System" application.

http://eyes.nasa.gov/download.html/