Theoretical Maximum Efficiencies of Optimized Slab and Spherical Betavoltaic Systems Utilizing Sulfur-35, Strontium-90, and Yttrium-90

Abstract

Monte Carlo simulations have been used for calculating the energy deposition of beta particles in the depletion region of a silicon carbide (SiC) betavoltaic cell along with the corresponding theoretical efficiencies. Three Monte Carlo codes were used in the study: GEANT4, PENELOPE, and MCNPX. These codes were used to examine the transportation of beta particles from 90Y, 90Sr, and 35S. Both the average beta energy from each source and the entire spectrum were modeled for calculating maximum theoretical energy deposition in both a spherical and slab geometry. A simulated depletion region was added in postprocessing containing the maximum energy deposited per micrometer. The calculated maximum efficiencies with the slab configuration model are approximately 1.95%, 0.30%, and 0.025% using monoenergetic average energy and 1.54%, 0.25%, and 0.019% using an energy spectrum for 35S, 90Sr, and 90Y, respectively. These efficiencies when using the spherical configuration model are 2.02%, 0.31%, and 0.023% using the monoenergetic average energy and 1.10%, 0.17%, and 0.013% using an energy spectrum for 35S, 90Sr, and 90Y, respectively.