Optimizing Thermoelectric Performance of p-Type Polycrystalline SnS Through Low-temperature Solid-State Reaction

The earth-abundant tin sulfide (SnS) has emerged as an ecologically sustainable alternative for the thermoelectric community recently. However, its wide bandgap (≈46 k_BT) is unfavorable for electrical performance, while the high vapor pressure of the S often results in a relatively low yield of synthesis. In this study, a synergistic strategy is devised to optimize the thermoelectric performance of polycrystalline SnS prepared via a low-temperature solid-state synthesis method. First, silver doping increases the hole carrier concentration (n) to ≈10¹⁹ cm⁻³. Subsequently, through selenium alloying, a dual-effect can be achieved: the bandgap is narrowed to increase the doping efficiency, while atomic point defects are introduced to lower the thermal conductivity. Ultimately, the polycrystalline Sn_0.98Ag_0.02S_0.55Se_0.45 attains a maximum ZT value of ≈0.9 at 873 K. The study indicates that promising thermoelectric performance can be obtained by a rapid synthesis method through a series of meticulously designed optimization strategies. This achievement offers novel insights and paves the way for the development of sulfide-based thermoelectrics.