I am not saying that space-based solar power is our go-to solution or that we need to bet on that to solve all other problems. I am saying that room to put solar panels is not the limiting factor of the tech. Cover deserts and oceans, use them as shades as you propose, and we have enough room to produce several times our consumption. I am only mentioning space only to express how limitless this factor is.

What are your solar panels built out off?

For the essential part mostly silicium, which is abundant on earth. Usually some structural metal, like aluminium or steel as well but many other materials work. You need small amounts of rare earths as impurities, many different tech exist. None has a problem of sourcing the minerals. We have enough proven reserves of these to switch to renewables. At this point the conversation usually switch to the environmental impact of resources extractions, which is not a tech problem, but a political one: we can make clean extraction. We make shitty extraction because it is legal to pay mineral from countries with no environmental protection and no labor rights but that's like saying farming can't be done sustainably because in some countries it is done by burning down forests to install ever-growing farms.

They never need maintenance?

Not a lot. Cleaning in some places, though a well designed system will have the rain for that. Weeding once in a while in luxuriant places. In some places panels are put flat, not at an angle, so that a dumb automated cleaning system is easy to put into place. It is less efficient per area of solar panel, but apparently as efficient per area of ground occupied. In space no, no maintenance (though here again, not advocating that directly)