The electrons then excite the gases whose excimer line is selected for the conversion of the radioactivity into a surrounding photovoltaic layer such that a theoretical lightweight, low-pressure, high-efficiency battery can be realized.
The surrounding weakly ionized plasma consists of gases or gas mixtures (such as krypton, argon, and xenon) with excimer lines such that a considerable amount of the energy of the beta electrons is converted into this light.
When the beta-emitting nuclides (e.g., krypton-85 or argon-39) emit beta particles, they excite their own electrons in the narrow excimer band at a minimum of thermal losses, so that this radiation is converted in a high-bandgap photovoltaic layer (e.g., in p-n diamond) very efficiently into electricity.
The advantage of this design is that precision electrode assemblies are not needed, and most beta particles escape the finely-divided bulk material to contribute to the battery's net power.
[citation needed] A simple betaphotovoltaic nuclear battery can be constructed from readily-available tritium vials (tritium-filled glass tubes coated with a radioluminescent phosphor) and solar cells.