I don't think 'solar sails' is the word you're looking for. Solar sails are used by lightweight spaceships to propel themselves through space using nothing more than the radiation pressure of the sun (or a concentrated laser beam). What you're looking for is probably 'orbital solar collector satellites' or some such.
Yes, it's designed as a very late game power solution, post rocket launch and only really useful once you've hit the point that scaling nuclear any further is a nuisance.