Assessment of the Contribution of Minority Carriers to the Thermo-electromotive Force of Thermoelectric Generators in the Case Where the Electrical Conductivity of the Majority Carriers Remains Very Large Compared to that of the Minority Carriers

Abstract

A theoretical prediction of the contribution to the thermo-electromotive force (thermo-EMF) of a thermocouple due to the minority charge carriers in both legs is presented. This prediction is made on the assumption that, at any time, the electrical conductivity of the majority charge carriers \(\sigma _M\) remains very large compared to the electrical conductivity of the minority carriers \(\sigma _m\) (\(\sigma _M\gg \sigma _m\)). The expression has also been analyzed in order to find strategies to reduce its negative impact on the thermo-EMF of the thermocouple. Finally, calculations were carried out in the case of the thermocouple made of silicon thermoelements. The results show that the presence of minority carriers in the thermocouple legs can either positively or negatively affect the generated thermo-EMF. Whenever the contribution is negative, its magnitude may be reduced by widening the bandgap of the N-type leg and/or narrowing that of the p-type leg, adjusting the length of the legs, or intensifying recombinations on the surfaces of the P-type leg