Not a fusion process, of course, but possibly competitive.  ARPA-E winner process:

http://web.mit.edu/newsoffice/2008/oxygen-0731.html
http://www.suncatalytix.com/tech.html

Break up the water while the sun shines, then recombine in a fuel cell when it doesn’t.  Uses phosphorus and cobalt.

Its fusion, just the sun kind
Still this is probably just the catalyst in the electrolyzer, nothing to do with solar cells themselves.

Fusion WILL be the way ... simply because it is so incredibly dense source of energy.
The rest is engineering ... and engineers are pretty good once the dollars are in place ...