Routes for advancing SnTe thermoelectrics

Conventional PbTe-based semiconductors have been leading the developments in the thermoelectrics community due to their rich capabilities in optimizing the electronic and phonon transport properties. However, growing environmental concerns related to Pb toxicity is guiding thermoelectrics research toward the lead-free route. As an alternative analog of PbTe, SnTe has recently attracted increasing research interest for thermoelectric energy conversion. The key challenges for enhancing the thermoelectric performance of SnTe to be comparable with that of p-type PbTe include decreases in the carrier concentration, energy offset between the light valence band (L band) and heavy valence band (Σ band), and lattice thermal conductivity. In this review, the recent progresses made in SnTe alloys are first outlined. Based on the insights gained into the intrinsic nonstoichiometry as well as the electronic and phonon transport properties of SnTe materials, fundamental and successful strategies focusing on confronting the challenges faced by figure-of-merit zT enhancement in SnTe are discussed and highlighted, aiming at providing a straightforward overview on the underlying physics of these effective strategies. Eventually, future challenges and outlook are summarized for boosting advancements in environment-friendly SnTe thermoelectric materials.