Decoupled electron and phonon transport in thermoelectric GeTe compounded with multi-walled carbon nanotubes

Abstract

With developing of thermoelectric (TE) performance, GeTe-based TE materials present great promising application at medium temperatures as a replacement for toxic PbTe. However, the further improvement of TE properties is severely constrained by the coupling of electron and phonon transport. In this study, we achieve decoupled electron and phonon transport by effectively creating a special phase boundary to scatter phonon but transmit electron by implanting multi-walled carbon nanotubes (MWCNTs) into Bi-doped GeTe. With the help of this decoupling mechanism, the power factor is effectively improved and reaches up to ∼4482 μW−1 m−1 K−2 at 673 K while the thermal conductivity shows an obvious drop to ∼1.27 W m−1 K−1 at 723 K, leading to an impressive increase in zT to a maximum value of ∼2.3 at 723 K. In particular, a competitive average zT value of ∼1.43 in the temperature range of 323–773 K is obtained, which is at a high level in lead-free GeTe-based materials. Our method could be used as a guidance for the decoupling of electron and phonon transport in other TE materials.