In the past few years, we have covered many decent solar chargers for smartphones. The Surfr for iPhone 6 happens to be a solar case with a 2700 mAh lithium polymer battery and an ultra-thin photovoltaic panel. The case is less than 15mm thick and provides your phone with battery juice on the go. You can also charge the case using a USB connection.
The Surfr for iPhone 6 offers 10 hours of extra talk time and does not get in your way. You can check it out in person at CES 2015.