Synergistically optimized electrical and thermal transport properties of polycrystalline SnSe via alloying SnS

SnSe crystals were reported to possess extraordinary thermoelectric performance, while the polycrystals were less marked due to the inferior carrier and phonon transport properties. Herein, we fully take advantage of the complex band structure and strong point scattering via alloying SnS. The carrier concentration and Seebeck coefficient were synergistically optimized via activating multiple valance bands and enlarging band effective mass, which contribute to a maximum power factor similar to 7.53 mu Wcm(-1)K(-2) at 793 K. Meanwhile, the lattice thermal conductivity was greatly reduced to similar to 0.92 Wm(-1)K(-1) due to the effective phonon scattering from point defects, as well demonstrated by the Callaway model. Combining a high power factor with low thermal conductivity, relatively high ZT of 1.2 at 793 K was obtained in polycrystalline Sn0.98Na0.02Se0.9S0.1. Our work demonstrates that alloying is simple yet effective approach for enhancing thermoelectric performance for polycrystalline SnSe, and SnSe system is one of promising thermoelectric candidates.