Stacking faults modulation for scattering optimization in GeTe-based thermoelectric materials

The enhancement of thermoelectric (TE) performance is essentially associated with optimizing the scattering effect of electron and phonon. Here, we demonstrate a stacking faults modulation strategy in GeTe materials to simultaneously realize high carrier mobility and low lattice thermal conductivity. Excess Cu doping in GeTe can significantly decrease the concentration of Ge vacancy layer and form a “vacancy/Cu–Cu/vacancy” sandwich-like stacking faults structure. As a result, the hole mobility is remarkably improved to nearly ~100 cm2 V−1 s−1 at room temperature due to the weakened carrier scattering from vacancy layer, which ensures superior electrical transport properties. Meanwhile, the sandwich-like stacking faults brings much stronger scattering effect on phonons, thus leading to extremely low lattice thermal conductivity of 0.38 W m−1 K−1. With synergistically optimized scattering effect on carriers and phonons, a peak thermoelectric figure of merit over 2.0 is achieved in Ge0.89Cu0.06Sb0.08Te at 750 K. This work provides an effective strategy to realize selective scattering of phonons and carriers through 2D defect modulation, and makes up the important piece of multi-scale microstructure tailoring for TE materials. [Display omitted] •Vacancy/Cu-Cu/Vacancy” sandwich-like structure is generated by excess Cu doping in GeTe.•Ge vacancy layer is depressed by excess Cu doping in GeTe material, leading to a high carrier mobility of ~100 cm2 V-1 s-1.•The minimum lattice thermal conductivity ~0.38 W m-1 K-1 is achieved due to phonon scattering of sandwich-like structure.