IIRC Sharp is also in the business of making solar panels, so this phone is more of a publicity stunt than a useful product. Think about the usage of a phone: you charge it up on your desk, you keep it in your pocket, and, for relatively brief moments, you hold it to your ear. These are not good uses of solar. If you want to incorporate solar into your lifestyle, mount a panel on your roof and use it to recharge your devices.
Of course, you live in France where more than 80% of the grid electricity comes from nuclear. So you are already most of the way, with or without solar.
Cat: the other white meat
Cat: the other white meat