The effects of electronic and photonic coupling on the performance of a photothermionic-photovoltaic hybrid solar device

Abstract

This work presents a detailed analysis of a photothermionic-photovoltaic hybrid solar device. The electrons in this hybrid device gain energy from both the solar photons and thermophotons generated within the device, and hence the device has the potential to offer a voltage boost compared to individual photothermionic or photovoltaic devices. We show that the gap size between the photothermionic emitter and the photovoltaic collector crucially affects the device performance due to the strong dependence of the electronic and photonic coupling strengths on this gap size. We also investigate how the current matching constraint between the thermionic and photovoltaic stages can affect the hybrid solar device performance by studying different hybrid device configurations. Moreover, the hybrid devices are compared with the single photothermionic solar device with a metallic collector. Interestingly, we observe that the addition of a photovoltaic stage meant to enable the hybrid device to capture the entire terrestrial solar spectrum does not necessarily lead to higher overall conversion efficiency.