Research Progress on Transport Mechanisms of Materials with Intrinsically High Thermoelectric Performance

Finding parent thermoelectric materials with a high figure of merit is a direction that people pursue. However, the interplay and constraints among the Seebeck coefficient, electrical conductivity, and thermal conductivity pose formidable challenges. In this review, the decoupling effect of anisotropic electronic energy band and multi-valley band structures are initially introduced on the Seebeck coefficient and electrical conductivity. Subsequently, an overview of how materials with a host-guest structure enable the coexistence of high electrical conductivity and low thermal conductivity through unique transport mechanisms is provided. Finally, deliberating on approaches to achieve intrinsic low lattice thermal conductivity, encompassing low dimensionality, low phonon group velocities, and substantial anharmonicity. Moreover, a detailed analysis is conducted to dissect the physical mechanisms through which strong higher-order anharmonicity restricts lattice thermal transport. It is believed that this review serves as a guiding resource for the quest for and design of efficient thermoelectric materials.