Yes, believe it or not, Apple initally filed for the patent in the third quater of 2008, to incorporate their aspirations of launching solar powered engineering for their iPod, iPad and iPhones.
The electric power generated from the solar cells could be used either to charge the rechargeable batteries or to directly power the main module or both.
This ingenius design of replacing the back metal panel with window will no doubt open the door for Apple to implement a double-sided panel design which will be solar powered.
Again, Apple will be the front runner with this very unique design! At this time, it is not known when these designs will be made available, but, it is definitely exciting! If you are curious on the entire design, please read more by clicking on this link.