Dynamic Regulation of Thermoelectric Transport Properties in GeTe via Phase Transition of VO 2

Abstract

GeTe-based compounds are promising candidates for medium-temperature thermoelectric applications, yet their performance is often constrained by intrinsically high hole concentrations. Optimizing the hole carrier concentration across the entire temperature range is essential for achieving outstanding thermoelectric performance and facilitating the practical application of GeTe-based materials. In this study, VO2 with an insulator-to-metal transition, is incorporated into Ge0.92Sb0.08Te to optimize both carrier and phonon transport over the whole temperature range. The energy filtering effect at the Ge0.92Sb0.08Te/VO2 interface leads to reduced carrier concentration and enhanced carrier mobility, which result in the optimized carrier transport properties. Moreover, the introduced VO2 precipitates, along with defects such as point defects and grain boundaries, as well as substantial lattice strains, enhance phonon scattering, leading to an ultralow lattice thermal conductivity. Furthermore, due to the insulator-to-metal transition of VO2 at approximately 341 K, the dynamic regulation of the carrier and phonon transport properties over the whole temperature range is achieved, giving rise to a high average ZT. As a result, a peak ZT of 2.0 at 603 K and an average ZT of 1.2 between 300 K and 773 K are achieved in the optimized sample, representing improvements of 40% and 30%, respectively, compared to pristine Ge0.92Sb0.08Te. This study demonstrates a feasible strategy for enhancing the performance of GeTe-based thermoelectric materials and offers new insights for optimizing the properties of thermoelectric materials in general.