Apple has had a patent approved related to the integration of solar charging in a device's touchscreen.
As opposed to the utilization of layers, the panel's electrodes will function as touch sensors and solar power collectors. It'll allow Apple to retain the thinness of its devices, while also offering the capability of being powered by the sun.
A management unit will decide whether the harvested energy applies power to the phone or, alternatively, be stored in the battery for future use. Apple's newly-granted U.S. Patent No. 8,368,654 for an "[i]ntegrated touch sensor and solar assembly" was filed back in 2008.