A Review of Polycrystalline SnSe Thermoelectric Materials: Progress and Prospects

As functional materials capable of direct thermoelectric energy conversion, thermoelectric materials hold immense promise for waste heat recovery and sustainable energy utilization. Through development in recent decades, many thermoelectric material systems with excellent performance have been developed. In alignment with the principles of circular economy and sustainable development, the search for new and efficient thermoelectric materials has become one of the most important directions of current research. SnSe has received much attention as an environmentally friendly and cost-effective thermoelectric material system. In particular, polycrystalline SnSe, with the advantages of facile preparation and stable mechanical properties, is suitable for large-scale industrial production. Here, we summarize the common preparation methods of polycrystalline SnSe in the decade of melting, mechanical alloying, and liquid-phase methods, as well as the strategies of property optimization such as microstructure design, grain boundary engineering, and band engineering. Finally, we provide perspectives on future research directions for polycrystalline SnSe to further improve thermoelectric performance and accelerate its practical applications.