Thermoelectronic Conversion of Solar Energy Using a Heterostructural Cathode

Abstract

The article presents a theoretical analysis of the features of the operation of a thermionic solar energy converter using a heterostructure cathode. A heterostructure is considered, into which a window layer with a sufficiently wide band gap and an absorbing layer, the band gap of which remains constant, are introduced. This makes it possible to greatly reduce the recombination losses at the contact surface. However, the presence of a wide band gap in the window layer leads to the emergence of a barrier for the forming photoelectrons, and this, in turn, leads to losses during energy conversion, since photons with energies less than the band gap stop working for energy conversion. That is, only part of the Sun’s energy will be converted into electrical energy — only part of the solar radiation spectrum is working. It is shown that this drawback can be overcome by creating a gradient of the band gap. This gradient makes it possible to create a reverse internal field, which reduces the height of the barrier at the contact surface, which increases the photoelectron yield and, ultimately, the overall conversion factor of the thermionic converter. Theoretical values are obtained for the output current and the conversion factor of a thermionic solar energy converter with a heterostructure cathode.