Investigating Thermoelectric Properties of GeTe Alloys with Multi Element Doping: Insights from High-Entropy Engineering

High-entropy engineering provides an effective strategy to enhance thermoelectric properties through increased lattice disorder induced by multielement doping. Recent multielement doping of GeTe-based alloys have significantly improved their thermoelectric performance, yet the vast compositional space of high-entropy GeTe makes identifying optimal compositions challenging. In this work, we investigate high-entropy GeTe alloys derived from the state-of-the-art Ge0.61Ag0.11Sb0.13Pb0.12Bi0.01Te system by partially adding Au to increase elemental and structural complexity without significantly degrading the electrical properties. Transmission electron microscopy confirms the presence of nanoscale lattice distortions and stacking faults that promote mass and strain fluctuations by enhancing phonon scattering. The Ge0.59Au0.02Ag0.11Sb0.13Pb0.12Bi0.01Te composition exhibits an ultralow lattice thermal conductivity of 0.22 W m-1 K-1 and achieves a maximum zT of 2.0 at 780 K. These findings demonstrate the effectiveness of high-entropy doping in tuning thermoelectric performance and advancing the development of next-generation GeTe-based thermoelectric materials.