I'm not sure I understand. If the charging device were to run on AA batteries and the phone runs on AA batteries, why not dispense with the middle man and just take extra AA batteries?

However, all the cell phones I am familiar with run on internal rechargeable batteries, not replaceable AA batteries, and the same thing applies to the non-solar charging devices for phones. They are basically one big rechargeable battery with some jacks to plug into.

As for the solar chargers, yes they can charge your phone, but they add extra weight and expense compared to the non-solar chargers, and are mostly worthwhile if you will be away from electrical outlets for a very extended period.