Although I believe that the best bet for the future lies with solar energy, I'd be extremely careful about making any big investments. Even if solar energy makes it to the big time, only a few of the companies involved will survive. Therefore you'd have to invest in a lot of the different companies hoping to hold the one that becomes your lottery ticket. Also, everyone else is thinking the same thing, putting their money into these companies and pushing the p/e ratios way up. Therefore none of the solar energy companies can be bought for a reasonable price.
FSLR is the most vulnerable of all solar stocks. I believe it can actually go out of business. Read this: http://www.seekingalpha.com/article/54614-first-solar-vulnerable-to-a-tellurium-shortage And this: http://www.seekingalpha.com/article/55959-the-tellurium-supernova And the latest should be SHOCKING because it clearly suggests a catastrophe in FSLR looming: http://www.seekingalpha.com/article/59854-investing-in-a-resource-constrained-world-part-i