Photon Amplification of Thermoelectronic Solar Energy Converters

Abstract

The work is devoted to a theoretical analysis of the efficiency of a thermionic device with photonic amplification. In analyzing the efficiency of photon-enhanced thermionic devices, two physical effects that were not considered in previous analyzes and their impact on the conversion efficiency of photon-enhanced thermionic devices were considered. The first effect is the influence of alternating voltage on the behavior of thermionic devices with photonic amplification and determining the maximum power value. The effect of charge carrier concentration on the maximum power was assessed using the balance of generation and loss of charge carriers. In this assessment, the assumption was made that the carrier concentration, temperature, and electrostatic potential are the same throughout the cathode. The effects of the negative space charge region were neglected. The assessment also assumed that the reverse current in the direction from the anode to the cathode affects the electron concentration in the conduction band. An expression for the efficiency of thermionic devices with photonic amplification is obtained and is determined as a function of the maximum operating voltage, cathode emission current and reverse anode current. The second important effect considered in the analysis is the thermal balance of the cathode. To account for this effect, a cathode configuration was considered in which the cathode is thermally isolated, i.e., there are no additional opportunities for heat removal from the cathode. This made it possible, based on the thermal balance, to determine the cathode temperature for a given input radiation flux and a given electrical operating point. It is shown that to determine the real efficiency under arbitrary operating conditions, the calculation of the electrical operating point must be carried out simultaneously with the cathode energy balance.