Can you quote a source for this figure?

I would expect that would be a wild generalization, there are some PV panels out there which have been rather less than energy efficient in their manufacture & transport (the plastic, glass & metal in them don't come naturally out of the ground) - does this figure take that into consideration?

PV panels were primarily developed as a convenient self-contained source of energy that didn't require replenishment, rather than the most eco friendly power source possible.

PV is good, but there are more energy efficient and low carbon ways of using solar energy than PV panels (including ways of generating electricity).
The larger solar generating plants don't use PV, because it doesn't generate as much power from the same amount of sunlight as say a solar powered electricity plant that derives the energy from heat such as: http://www.stirlingenergy.com/