Panels absolutely, their price is more and more dominated by installation costs. You can probably use automation to bring that down as well, especially for large-scale installations. Not sure if that requires AI research though, it's more an engineering and funding challenge.

Batteries are still open. While they do get cheaper, there is still a lot of room to improve. And battery chemistry is something where a lot of research, trial and error, healthy intuition is necessary. I'd say that is more a field where an AI based approach might make sense.