Theoretical Calculation For The Energy Conversion Unit Of Isotope Battery Based On Epitaxial Single Crystal Diamond

Diamond materials have wide forbidden band,strong anti-radiation ability,good chemical inertness,so the Schottky junction isotope battery prepared with them could possess high output voltage and energy conversion efficiency,well anti-interference performance,small effect by outside temperature,pressure and electromagnetic field which result in its long-term,stable work feature,and broad application prospect.In this thesis,Geant4 software based on Monte Carlo numerical calculation method has been used to simulate and calculate the energy deposition as well as the device performance of the isotope battery energy conversion unit with Schottky diode structure based on epitaxial single-crystal diamond,which results could provide theoretical basis and guidance for further practical device design.First,the energy deposition in schottky junction metals of isotopic cell energy exchange unit under different radioactive sources was simulated and calculated using Geant4 software.The results indicate the radioactive sources adopted Ni-63,H-3,and Pm-147 respectively possess different main energy loss manner corresponding to Cu,Au and Ni schottky metal,in which for Ni-63 source the energy of reflection and deposition has the almost similar contribution,while for H-3 and Pm-147 the reflection ratio is far greater than the part dedicative by energy deposition.Furthermore,to make the loss energy ratio coming from reflection and deposition below a assumed threshold?10%?,the required corresponding thickness of schottky metal are different:for Ni-63source,the maximum thickness of Cu,Au and Ni is 30nm,20nm and 30nm respectively;for H-3 source the critical thickness all is 100nm to Cu,Au and Ni;while for Pm-147 source,the corresponding thickness is 20nm,10nm and 10nm respectively to three different metals.Further simulation of energy deposition in the diamond layer for the beta particle passed through the Schottky metal has also been accomplished,which results show that the metal/diamond composite layer could block the penetration of beta ray to a large extent,and the energy deposition of beta ray in diamond decays in an exponential manner with the increase of incident depth.For the H-3 source respectively corresponding to Schottky metal Cu,Au and Ni which critical thickness all is 100nm,under this precondition,to achieve that the energy of the beta particles passed through the metal layer could completely deposited in the diamond layer,the thickness of the corresponding diamond layer will exceed 1.4um.Similarly for the Ni-63 source,corresponding to Cu the thickness of the diamond layer need be greater than 10um,and for Au and Ni,the diamond thickness should exceed 10um.For the Pm-147 source,corresponding to Cu,Au and Ni,the necessary diamond layer thickness respectively are 11um,12um and 12um.On this basis,through fitting the energy deposition curve in diamond for three different beta radiation sources,combined with the theoretical formula derivation of the electric output parameters,including short-circuit current,open circuit voltage,the fill factor and energy conversion efficiency of Schottky betavoltaic battery,as well as their relationship with the doping concentration of boron in diamond,the electric output parameters of the isotope battery energy conversion unit with Schottky diode structure based on epitaxial single-crystal diamond were calculated.The obtained results show that when the doped boron concentration is 1×10¹³cm^-3 in diamond,the width of the depletion region achieve to 8um which correspond to the short-circuit current,open circuit voltage,and fill factor and conversion efficiency reaching a relatively large value,and the maximum conversion efficiency could come to 4.1%:corresponding Ni-63 radiation source,the short circuit current is 6.55nA,voltage is0.37V,the fill factor is 0.588,conversion efficiency is 4.1%;corresponding H-3radiation source,the short circuit current is 0.547nA,voltage is 0.037V,the fill factor is0.479,conversion efficiency is 2.9%;and corresponding Pm-147 radiation source the short circuit current is 3.46nA,voltage is 0.074V,the fill factor is 0.498,and the conversion efficiency is 2.43%.