Enhancing Thermoelectric Efficiency in GeTe via Tailored Alloying and Band Engineering

Abstract

The development of advanced thermoelectric materials stands as a cornerstone in the pursuit of sustainable energy technologies, offering transformative potential for waste heat recovery and renewable energy systems. Despite the promising attributes of GeTe as a midtemperature p-type thermoelectric material, its practical efficiency remains constrained by inherent challenges, namely, its high lattice thermal conductivity and suboptimal carrier concentration. In this study, we introduce an innovative dual-strategy framework that seamlessly integrates tailored alloying and band convergence to achieve a profound decoupling of electrical and thermal transport properties in GeTe. Through systematic investigations of Se and Pb alloying, we demonstrate that Se alloying effectively reduces lattice thermal conductivity by enhancing phonon scattering, while maintaining superior carrier mobility─outperforming Pb alloying in this regard. Moreover, the strategic incorporation of Sb doping at Ge sites not only refines carrier concentration to optimal levels but also enhances crystal symmetry, thereby fostering valence band convergence and significantly elevating the Seebeck coefficient─a critical metric for thermoelectric performance. The synergistic implementation of these advanced strategies culminates in the optimized composition Ge_0.9Sb_0.1Te_0.9Se_0.1, which attains a remarkable peak ZT value of approximately 1.8 at 773 K and maintains an impressive average ZT of 1.1 across the temperature range 300–773 K. These results underscore the transformative impact of our approach on achieving state-of-the-art thermoelectric performance. This work illuminates the pivotal role of tailored alloying and symmetry-driven band engineering in advancing thermoelectric materials.