In the future, will solar energy be the main source of our power?

I realize that current solar panels are not that efficient. However, is it possible that they will eventually (in 20-30 years) be efficient enough to provide most of America’s energy needs (75% or more)? The reason why I ask is that I once saw an TV interview in which some researcher from MIT was questioned about solar panels. He basically said that solar panel efficiency will double every two years.

Is this true? If possible, could you please cite an article or a reliable source?