Quasi-commercial production of SnS-based nanosheets with enhanced thermoelectric performance via a wet chemical synthesis

Abstract Tin sulfide (SnS) is a low-cost, earth-abundant, and eco-friendly thermoelectric (TE) material whose layered orthorhombic structure is similar to that of SnSe; however, current studies on SnS are limited because of its difficult synthesis due to the use of volatile sulfur, and its thermoelectric figure of merit (zT) is also low because of its intrinsically low electrical conductivity. Herein, we present a facile wet chemical synthesis to prepare uniform and well-dispersed SnS nanosheet crystals. Low-rate initial production with 3.5 L solvent was performed to obtain high-quality crystals, and also to adapt the process to commercial preparation. The carrier concentrations were enhanced from 3.2 × 1018 cm−3 to 4.8 × 1019 cm−3 (at 873 K) step-by-step via increasing Sn vacancies, adding SnSe, and embedding Ag atoms. The maximum power factor (PF) at 873 K of 0.48 × 10−3 W⋅m−1K−2 was achieved in the selenium-silver co-doped sample, which presented a state-of-the-art value for the polycrystalline SnS. Correspondingly, the lattice thermal conductivities ( κ L ) decreased from 0.8 W⋅m−1K−1 to 0.47 W⋅m−1K−1 (at 873 K) due to enhanced phonon scattering. The highest zT was 0.80 at 873 K, which is about 5 or 6 times higher than those of the pristine SnS(1:1) or SnS(1:0.8) samples. These findings provide a novel method to prepare high-quality and high-performance TE semiconductors via a wet chemical synthesis.