14C diamond as energy converting material in betavoltaic battery: A first principles study

The application of radioactive semiconductors is a potential way to improve the performance of betavoltaic battery. The stability and band structure of decayed 14C diamond are investigated by density functional theory. After the decay, the 14C atoms are substituted by nitrogen atoms, and it can be seen that the corresponding C63N1 and C62N2 structures have larger lattice constants and become more unstable. The C63N1 structure is a metallic system instead of an indirect bandgap semiconductor. Different C62N2 configurations have either metallic or indirect bandgap semiconductor properties, and the bandgaps are significantly lower than those of pure diamond. The 14C diamond–12C diamond betavoltaic battery switches between a pn-junction and p-type Schottky diode with higher short-circuit current.