Theoretical Analysis of InGaN Solar Energy Converters Based on Photon-Enhanced Thermionic Emission

Abstract

Photon-enhanced thermionic emission (PETE) is an efficient solar energy conversion mechanism that combines photovoltaic effects and thermionic emissions. In this study, a diffusion–emission model of electrons for the InGaN cathode was deduced based on one-dimensional continuity equations. The temperature dependence of the excess electron concentration, current density, and conversion efficiency at different cathode electron affinities was simulated, and the performance of the PETE converter under isothermal and nonisothermal state was compared. The results show that the improvement in conversion efficiency under isothermal condition was limited by the increase in anode temperature and reached the maximum of ~22% at an electron affinity of 0.56–0.59 eV and the operating temperature of 710–740 K. When the anode temperature was 500 K, the conversion efficiency increased with the increase in the electron affinity and exceeded the maximum value of the isothermal state at 0.6 eV. We explored the behavior of the converter at bias voltages as well as the determination of the maximum conversion efficiency point. The open-circuit voltage in the isothermal state was lower than that in the nonisothermal state, and the output voltage at the maximum conversion efficiency was eventually greater than the flat-band voltage.