Significant band engineering effect of YbTe for high performance thermoelectric PbTe

Abstract

Alloying, to minimize the energy offset between the two valence bands of PbTe, has been well demonstrated to yield thermoelectric performance enhancements. Distinct from the currently known alloying species such as MnTe, MgTe, CdTe, PbSe and PbS, where the high performance partially comes from the alloy phonon scattering as well as because of the high alloying content of ≥3%, YbTe, even with a concentration as low as 1%, is found here to have an extraordinary role in engineering the band structure to achieve a thermoelectric figure of merit, zT, approaching 1.8, without relying on strong phonon scattering. This work demonstrates new insight into the further improvement of thermoelectric materials, because this strategy leaves the feasibility of lattice thermal conductivity reduction nearly unaffected, which can be obtained by other well-demonstrated approaches such as nanostructuring.