Performance improvements and parametric design strategies of an updated thermionic-photovoltaic converter

A novel model of the hybrid converter consisting of a thermionic generator with a graphene-based anode and a photovoltaic cell is proposed. The power output densities and efficiencies of two single subsystems and the hybrid converter are derived. The effects of the emitter temperature, voltage outputs, and band gap energy on the performance of the hybrid converter are analyzed. The optimally operating bounds of several critical parameters including the power output density, efficiency, and voltage outputs of the hybrid converter are determined. It is found that in the optimally working region, the performance of the hybrid converter with a graphene-based anode is obviously better than that with a metallic anode. It is also found that in a certain temperature range, the maximum efficiency and power output density of the hybrid converter significantly exceed those of the thermionic generator or photovoltaic cell.