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Couldn't we have a lead box lined with these radiation to electricity converters with a small amount of radioactive material in the center, and have an energy generating device that would last for thousands or even millions of years? Imagine putting the sun in a box lined with solar cells, but on a much smaller scale.
Is there a reason this wouldn't work?
There is the nano/nuclear diamond battery thing too, which is supposed to work like this but apparently produces very little energy if any
https://ndb.technology/
I worked up the energy to google. Turns out it's not a photovoltaic (gamma-voltaic?) anyway, it's a betavoltaic. I guess that makes more sense than the rubbish capture cross section of high energy light.