Various forms of solar are probably one of our better bets, though I'm not convinced that large chunks of the recent gains don't come from massive effective subsidy from China and eventually the cost of the materials themselves could become insignificant compared to complexity and maintenance and end-of-life-recycling cost which are not likely to decrease much. Though battery performance... I haven't seen anything about it that even looks vaguely exponential.
though I'm not convinced that large chunks of the recent gains
I get the impression that most of the "recent gains" consist of forcing the utilities to take it and either subsidizing the price difference or passing the cost on to the customer. At least, the parties involved act like they believe this while attempting to deny it.
You know the drill - If it's worth saying, but not worth its own post (even in Discussion), then it goes here.