Asklemmy

Yep, it's called a "radioisotope thermoelectric generator". Mostly used on satellites.

Lot of comments about RTGs, but I don't think that's what OP is asking. RTGs convert heat to electricity, same as a conventional power plants

they just do it in a solid state way instead of steam. In RTGs it doesn't matter where the heat comes from; they are not really analogous to solar cells, as the title asks.

In fact, there are consumer products that use the same technology

you can buy a little electric fan that sits on top of a wood stove and, once up to temp, will start spinning. The electricity is generated by the thermal gradient using heat from the stove, essentially the same as an RTG.

Yup, RTGs exist, but they're impractical for most terrestrial use cases. The problem is that any isotope that's energetic enough to generate meaningful amounts of energy is also going to be somewhere between quite dangerous and insanely dangerous if the container is breached. And unless there are very strong protocols in place for handling the RTG, on a long enough timeline, there's basically guaranteed to be a nuclear accident.

Yes, with RTGs. They are used on mars rovers, for example.

No one has directly answered your question.

The answer is yes, you can create photovoltaic cells better optimise to pick up high energy light such as that from nuclear decay (gamma radiation). However, the power generated by photovoltaics is limited more by intensity of the light, and not the energy per photon (wavelength). For physical reasons is hard to capture the energy of high energy light, so gamma photovoltaics are low power concepts.

There is an idea going around to grow diamond with c14 and also harvest that c14 decay with a diamond based photovoltaic. Making everlasting batteries, albeit radioactive and microwatt. (Specifics are probably wrong, working from memory.)

There is the nano/nuclear diamond battery thing too, which is supposed to work like this but apparently produces very little energy if any

Yes and we already have and use them. Albeit only on NASA probes leaving earth.

Both of the curiosity rovers use this as their power plant. A bunch of plutonium sits in that little tail like stub on them and generates perpetual power for them.