Ground based solar has a capacity factor of about ~25% depending on location, while a space based installation would have nearly a 100% capacity factor. So to generate the same amount of energy per year you need about 4x as many panels on the ground. I probably should not have said power but instead something like exajoules/year.
Another important issue is that in space, PV can be extremely thin. The actual active layer of semiconductor can be maybe 50 microns (for silicon) or less than 1 micron (for CdTe). This also suggests solar-powered electric propulsion in space can have high acceleration, limited by heat dissipation in the engine.
