And who manufactures these photovoltaic cells at what cost? Considering the amount of energy that would be needed to make the cells and the work involved in setting up a vast network of them to generate the needed power to separate Hydrogen and oxygen from water, I'm not sure that the energy debt could be paid back.
Photo-cells can be made that are fairly resistant to damage now but thats only been true for a few years and they are pretty low yield. A cell farm has to be set so the cells follow the sun for maximum output. This requires sophisticated tracking gear and panels mounted on bearings.
The desert environment is not kind to such things; sand and dust get into everything and maintainence is a nightmare. Ask anyone who has worked in North Africa or was in Desert Storm.
IF all the problems could be overcome at reasonable expense in time and energy, it's a nice idea.