I think it's still possible to sign up for this free online class:
http://class.stanford.edu/solar/Fall2012/
The intro says that they will talk about the details of how
photovoltaics work. They will also talk about batteries and fuel
cells. No textbook, it is based on video lectures and an online
forum. They quiz you while the lecture is being given and there are
homework assignments, and then a final exam.