Solar power is the future of everything, right? Maybe in the long run, but Nokia has shown that the technology isn't quite up to scratch when it comes to powering smartphones permanently.
The Finnish company sent mobile prototypes packing solar panels on the back all around the world, including Kenya and the Arctic Circle to test the viability of solar power for mobiles. Unfortunately, the best results were barely enough to keep the phone in standby mode.
That's not to say that we'll never see a completely solar powered smartphone, of course. Just that it's unlikely we'll see one any time soon.