Recent Advances in Ultrahigh Thermoelectric Performance Material SnSe

This perspective discusses the surprising discovery and development of SnSe thermoelectrics. Undoped, hole-doped, and electron-doped SnSe single crystals have successively represented an extraordinarily high thermoelectric figure of merit (ZT) ranging from 2.6 to 2.9, revitalizing efforts on finding new high-performance thermoelectric systems. Their unprecedented performance is mainly attributed to ultralow thermal conductivity arising from the uniquely anisotropic and anharmonic crystal chemistry of SnSe. Soon after the publications on SnSe single crystals, substantial debates were raised on their thermoelectric performance, especially on truth in ultralow thermal conductivity. Very recently, polycrystalline SnSe samples were synthesized, exhibiting lower lattice thermal conductivity and higher ZT than the single crystal samples. This work clearly addressed many questions that have arisen on the intrinsic thermal and charge transport properties of SnSe-based materials. It shows a peak ZT of ~3.1 at 783 K and an average ZT of ~2.0 from 400 to 783 K, which are the record-breaking performances of all bulk thermoelectric materials in any form ever reported.