LAUSR

Abstract The space charges and the radiation heat in the interelectrode space have been thought as the sources of the major irreversible losses of micro-scale vacuum gap thermionic emission devices. By focusing on the photo-enhanced thermionic emission (PETE) solar cell, the space-dependent expressions of the space charge effect and near field radiation loss are derived. The coupled balance equations of energy and carrier are considered to determine the carrier concentration and temperature of the cathode. The space charge limited regions and principal energy fluxes of the cathode are discussed at different interelectrode spaces and environmental changes. The maximum efficiency is calculated by optimizing the operating voltage and interelectrode space. The optimal gap ranges are also revealed, which is comparable to the characteristic wavelength of thermal radiation given by Wien’s displacement law. Our investigation will provide an effective way to optimally design the structure of the PETE device.