Multifunctional Roles of Vacancy Defects in Advancing Thermoelectric Materials

The perception of vacancies has evolved from passive scattering centers to multifunctional defects capable of actively modulating material properties in the thermoelectric (TE) field. By tailoring band structure, carrier concentration, and phonon dynamics, vacancies offer a versatile approach to achieving enhanced TE performance. A systematic understanding of vacancy formation, characterization, and functionality is therefore essential for the rational design of next-generation high-performance TE materials. In this review, we summarize recent advances in vacancy engineering for thermoelectrics, classifying vacancies according to their functional roles, surveying advanced characterization techniques for their identification, emphasizing the predictive and guiding capabilities of computational methods, and detailing strategies for precise vacancy control. Additionally, the latest developments regarding the impact of vacancies on electronic transport, phonon scattering, and mechanical properties are systematically discussed. Finally, we highlight the major challenges and future prospects in vacancy engineering, aiming to provide a foundation for the rational design of high-performance functional materials via vacancy-mediated defect strategies.