When asked to list energy sources the standard come to mind: fossil fuels and nuclear fission for non renewable and solar, wind, tidal, etc for renewable sources. A source that is not commonly though of is radioisotope thermoelectric generators. These generators work by completely surrounding a radioactive source and capturing every decay particle that occurs. This causes heat to be generated that then using the thermoelectric effect (heat can cause a current to flow) produces an electric current. An even less known version of this again is the concept of betavoltaics. This is a unique scenario where instead of heat, the beta particles when passing through a semiconductor promote electrons into the valence band creating an electron hole pair that then recombined causing an electron flow. Alpha voltaics exist too, but the massive alpha particles break down the cell they’re put in hundreds of times faster than the much lighter beta radiation. These sources would hopefully be used where it would be impractical to access a device for a long period of time. Remote weather stations, pacemakers and spaceships have all used nuclear generators in this form for some time.
However all currently produced betavoltaics whether they are in a lab or on the marked do not have an efficiency that’s ever greater than 3%. A study has been produced focusing on how to improve that number. The fuel they chose to look at was strontium-90 as it is a common product of nuclear fission and itself provides a lot of energy as it decays. The primary idea was to cut down on size and unneeded mass. Since the beta radiation gets absorbed by the semiconductor and the extra bremsstrahlung radiation can itself go on to produce more electron hole pairs the shielding does not need to protect from the radiation of the device. If the exact dimensions could be designed to match the radiation penetration depth it may be possible to create a betavoltaic cell with an efficiency of 10% rather than the original 3%. Designing a working prototype is an essential next step in order to see how promising this idea actually is in practice.