There's an abundence of sites that explain solar energy in-depth and it can be hard to wade through them all. There are a few sites that are especially helpful and are the best place to start for more information.
Solar Energy Industries Association: SEIA offers an indsutry-insider view of the growth of solar energy and was recommened as a source by Patrick Seehan of Florida's Office of Energy.
U.S. Department of Energy: For detailed information, including charts and reports of solar use and growth, and advice for average consumers who want to begin using solar energy.
U.S. Energy Information Administration: A wealth of information, including annual reports and forecasts, that cover things energy are available through the EIA.
EIA 2013 Report: The 2013 report offers the most complete and up-to-date information on energy in the United States.
Wikipedia: While some teachers may still not approve of using Wikipedia as a source, the article on solar cells is ripe with good, detailed information and links to additional sources.