Investigation of factors influencing the efficiency of nuclear batteries

In this thesis, the conversion of the kinetic energy of beta particles emitted from a radioactive isotope to electricity is investigated by using the direct and indirect conversion methods. In the experimental part, analysis of the effects of low-activity radiation from Pm147 and Sr90 beta sources, two different phosphors and graphene on Si photovoltaic cell is performed. Phosphor layers with different mass thicknesses are prepared from ZnS:CuCl and SrAl2O4:Eu2+,Dy3+ phosphor powders. The electrical performances of direct and indirect nuclear battery models are analyzed by measuring short-circuit current and open-circuit voltage. Furthermore, the time-dependent variation of the short-circuit current during the beta irradiation is researched. The most efficient battery model is determined as Pm147/SrAl2O4:Eu2+,Dy3+/PV cell. In the theoretical part, betavoltaic battery designs are modeled using the p-n homojunctions, p-n heterojunctions, and Ni63, Pm147 beta sources by considering the parameters affecting the efficiency. A theoretical investigation of the electrical performances has been carried out on Si, GaP, GaN, GaP-Si, and GaN-Si betavoltaic batteries. In addition, the effects of doping concentration and junction depth on the maximum power are examined. The heterojunction photovoltaic cells are preferred to increase the collection efficiency and the power in the betavoltaic battery according to our calculations. By optimizing the doping concentration and junction depth, high-efficient heterojunction betavoltaic batteries are achieved.