Theoretical Bound on the Thermoelectric Figure of Merit of Two-Band Semiconductors

Abstract

The Simon two‐band semiconductor model is investigated further theoretically to determine whether a finite upper bound can be imposed on the thermoelectric figure of merit. It is shown that limitations on the adjustability of the Fermi level and use of reasonable physical values for the band parameters do lead to a finite upper bound for the two‐band model which is of the same order of magnitude as that derived earlier by Rittner for a one‐band model. The former can be severalfold higher than the latter but only at pathologically high values of the effective mass ratio m_h/m_e. Other factors which favor a high value of the upper bound are discussed.