The Thermoelectric Properties of SnSe Continue to Surprise: Extraordinary Electron and Phonon Transport

Thermoelectric technology enables the harvest of waste heat and its direct conversion into electricity. Most well-developed strategies aimed at enhancing thermoelectric performance are based on isotropic bulk materials. The strong coupling relationships in thermoelectric parameters make it difficult to optimize electron or phonon transport solely to realize high thermoelectric performance. Recently, many emerging materials with 2D structures elucidate superior thermoelectric properties originating from their anisotropic structures and transport features. However, the strategies to enhance thermoelectric performance for these materials with 2D structures are still ambiguous. In this Perspective, SnSe was selected as an example with 2D structures; the remarkable electron and phonon transport of SnSe are summarized for several aspects, including crystal structure, anharmonicity, multiple valence band structure, continuous phase transition, and 3D charge and 2D phonon transport. These illuminating discoveries in SnSe could provide routes to seek promising thermoelectric materials with 2D structures and enhance the thermoelectric performance.