Solar at Mars is not that big of a deal. You need bigger panels, but with the massive increases in efficiency you get each machine generation (roughly 18 months). This great write up on the ISS wings says that the ISS uses an acre of panels to generate 90Kw of power. These panels are using cutting edge engineering from the early 2000's and are not as efficient as the new stuff that they are using on, for example, Juno. the Juno panels would generate 14Kw if at earth, say 1/2 that at Mars. The thing holding you back more than anything really is the battery. Batteries are big bulky, chemical soups that are not growing in efficiency nearly as fast as the Solar stuff. As as your spacecraft will go through eclipses in orbit around a body, you need batteries to store charge. This is one reason they don't want to use solar panels on the lunar surface; they get 14 straight days of night, so you need to double power and have a massive energy sink to store the excess.