Tesla patented a device for gathering energy from light, using the photoelectric effect. (US 685,957 - Apparatus for the Utilization of Radiant Energy):
Basically just a sheet of "highly polished or amalgamated" metal (top) connected to a capacitor (the ⊔⊓ shapes) connected to the Earth. (The other stuff on the right of the image is a load intermittently driven when the charge on the capacitor rises high enough.)
The patent says it would be able to collect energy from the sun. Would this actually work? Why or why not? Does it need to be in a vacuum? The patent seems to say that it works better in a vacuum but that it is not required. Would the plate stay charged after electrons are thrown off, or would they be attracted and drift back to it and neutralize it? How does the capacitor to earth make this better than a plate hanging in space? It allows more charge to be stored for the same work function voltage of the metal?
The patent demonstrates that he doesn't understand the cause of the photoelectric effect ("sources of such radiant energy throw off with great velocity minute particles of matter which are strongly electrified, and therefore capable of charging an electrical conductor"), but he understands the results.
(Incidentally, I have tried building this with a piece of aluminum foil, electrolytic cap, and wire strong enough to stick a few inches into the ground. I didn't see any voltage with a multimeter in bright sunlight.)