Advances in Ag₂Se-based thermoelectrics from materials to applications

Thermoelectric materials and their devices can realize the solid-state energy conversion between thermal and electrical energy, therefore serving as a promising alternative to conventional fossil fuels for energy supply. As one promising thermoelectric material, Ag₂Se-based semiconductors exhibit considerably high thermoelectric performance at near-room temperatures and show considerable application potential in self-powering wearable electronics and solid-state refrigeration. Considering the fast development in Ag₂Se-based thermoelectrics, a timely review for summarizing their progress, challenges, and outlook is of significance. In this review, we first focus on the fundamentals of Ag₂Se, including its thermodynamics, crystal structures, band structures, liquid-like behaviors, and mechanical properties. Then, the advanced strategies employed in Ag₂Se-based thermoelectric materials for improving their thermoelectric and mechanical properties are summarized. Besides, this review overviews the development of device designs from computational simulations, fabrication technology, and novel applications. In the end, we discuss the major controversies, challenges, and outlook for the future development of Ag₂Se-based thermoelectrics.