Some remarks on the Peltier heat in the thermoelectric phenomena

Abstract

In the present article, we conceptually develop some understanding of the Peltier heat resulting at the rectifying junction between a metal and an n-type semiconductor with a depleted space charge layer ("the Schottky barrier") as well as two Ohmic contacts between a metal and an n-type semiconductor with an enriched space charge layer, and two dissimilar metals chosen as three instructive examples via "the thought experiment," based upon the energy band diagram of metal and semiconductor. Additionally, we briefly discussed on the difference between the contact potential and diffusion potential, both of which proved to be a thermodynamic reversible potential as well that influences greatly the Peltier coefficient. We concluded that the reduction in the kinetic energy of more energetic electrons passing through the rectifying junction as well as the two Ohmic contacts is accompanied by the Peltier heat evolution. By contrast, the enhancement in the kinetic energy of less energetic electrons passing through the rectifying junction as well as the two Ohmic contacts is associated with the Peltier heat absorption. The Peltier heat evolution and absorption resulting at the rectifying junction as well as the two Ohmic contacts can be well understood in terms of reduction/enhancement in the kinetic energy of electrons crossing the junction, respectively, under the isothermal constraint of a couple of junctions. The rectifying junctions provide Peltier effects more markedly than the two Ohmic contacts. This idea provides in particular a basis for the thermoelectric generator (batteries) and it can be extended to other rectifying junctions such as a p-n junction and another Ohmic contact between metal and p-type semiconductor with an enriched space charge layer.