Oh, it's just a thermopile put out in the sun.

I can see why it never caught on then. You'd be relying on the difference in temperature between the hot side of a thing painted black put in the sun and the cool side in the shade. The amount of energy you'd get from such a setup would be infinitecimal. I'd expect you'd need to do an absurd amount of work and use an absurd amount of material just to power a single house.

The amount of energy it would take to build a "solar cell" thermopile that'd generate 1.5v with a quite high internal resistance would probably be in the megawatt-hours, likely from coal and oil.