A core-shell structure to realize high thermoelectric performance in Fe and Sb co-doped GeTe materials

GeTe is a promising medium-temperature thermoelectric material. However, an excessively high concentration of Ge holes leads to a high hole carrier concentration, which can degrade its performance. Though carrier concentration reduction via doping has been pursued as a principal optimization approach, the strong interdependence between key transport parameters and carrier concentration severely limited the overall enhancement efficacy. In this work, a simple composite method is employed to achieve synergistic optimization of carrier concentration and carrier mobility, thereby increasing the power factor and reducing the lattice thermal conductivity. Sb and Fe form a core-shell structure, which effectively scatters phonons and reduces the lattice thermal conductivity, achieving a minimum value of 0.59 W⸱m –1 ⸱K –1 at 723 K. Additionally, Fe doping enhances the effective mass, improves the Seebeck coefficient, and significantly boosts the power factor, which reaches a peak value of 43.0 μW⸱cm –1 ⸱K –2 at 623 K. The results demonstrate that the sample Ge 0.885 Sb 0.1 Fe 0.015 Te achieves a maximum zT of approximately 2.13 at 723 K and an average zT ( zT avg ) of 1.43 within the temperature range of 323 K to 773 K. This work provides an effective path to enhance the performance of GeTe-based thermoelectric materials. • Core-shell structure in GeTe improves thermoelectric performance. • Fe doping optimizes carrier concentration and enhances power factor (43 μW⸱cm –1 ⸱K –2 ). • Lattice thermal conductivity reduced to 0.59 W⸱m –1 ⸱K –1 via phonon scattering. • Strategy effectively decouples electrical and thermal transport for high zT.