Here is the fact of life for solar charging. The average for the earth is 600 watts per square meter of solar power. We can only achieve about 10% efficiency in a solar panel so that is 60 watts. If you made the entire back of an iPone a solar panel the size is less than 15 square inches. A square meter is 1550 square inches. So that is 1/100 of 60 watts which is .6 watts. The iPhone battery is a total of 5.45 watt hours. So bottom line is that in good sunlight you could keep the iphone running but there is nothing left to charge the battery. so it could work when it was in your pocket, at night etc.
However wireless pad charging is another subject and it was prepared for but not release on SIII That is something Apple could do and get a little leg up