Effect of multisite alloying and chloride doping for realizing a high thermoelectric performance in misfit-layered chalcogenide

Abstract Misfit-layered chalcogenide has captured large attention due to its unique opportunity for optimizing figure of merit zT originating from the natural superlattice structure. Existing strategies mainly focus on single element doping at cation site, while multisite alloying, especially for the doping at anion site, has not yet properly understood. In this work, chloride doping at anion site as a novel method is utilized to create excess electrons for manipulating the carrier concentration, thus achieving an advancement on electronic performance (up to 1.0 mW K−2 m−1) by ∼35% in oriented textured (SnS)1.2(TiS2)2 alloys. Such a chloride anion doping also enables a reduction on the lattice thermal conductivity to 0.82 and 0.35 W K−1 m−1 in the in-plane and out-of-plane directions, respectively. In addition, the multisite alloying strengthen the phonon scattering for a further reduction on lattice thermal conductivity, thus leading to an enhancement of thermoelectric performance. Consequently, a record zT∼0.45 is realized in the in-plane direction, which demonstrates (SnS)1.2(TiS2)2 based material as a promising thermoelectric candidate and the multisite alloying as an effective strategy for zT enhancement.