Thorium-229ml /m2-powered heterojunction GRPVCs: an interface between nuclear and semiconductor physics

摘要

This paper studies the performance of heterojunction GRPVCs (gamma ray photovoltaic cells) when the semiconductor materials are illuminated by the γ-photons emanating from the two nuclear isomers of Th-229: Th-229ml (E_γ = 3.5 eV, T_(1/2) = 45 h) and Th-229m2 (E_γ = 7.6 eV, T_(1/2) = 5 h). Contour graphs of constant efficiency, η, and open circuit voltage, V_(oc), in the E_(g1)-E_(g2) plane display the optimal point of operation; hence the maximal η and V_(oc) of the heterojunction GRPVC. Similarly, contour graphs of constant η and V_(oc) in the E_(γ1)-E_(γ2) plane, for given semiconductor energy gaps and other parameters, display the optimal points of operation; hence suggests the features of nuclear isomers needed to be used. It is found that heterojunction GRPVCs that employ two different nuclear isomers, and semiconductor energy gaps matching the γ-photon energy, are less efficient compared to homojunction ones that are illuminated by single nuclear isomers. A 0.40 m diameter GRPVC with 1 mole of eachrn isomeric state of Th-229 produces an output V_(oc) = 6 V at maximum efficiency η = 45% initially occurring at the point (E_(g1) - 7.6 eV, E_(g2) = 7.6 eV), which represents a homojunction configuration. When illuminated only by the isomer Th-229m2 the corresponding homojunction efficiency and open circuit voltage are η = 63.4% and V_(oc) - 6.673 V, respectively. We also report on results of remarkably high maximum output power,P_(max), and photo-generated current, J_1, for homojunction and heterojunction configurations of GRPVCs.