Morphology and Texture Engineering Enhancing Thermoelectric Performance of Solvothermal Synthesized Ultralarge SnS Microcrystal

With intrinsically strong anisotropy, layer-structured SnS and SnSe-based thermoelectric materials are attracting extensive attention. In this study, we synthesized ultralarge SnS microcrystal through a facile solvothermal method. It is found that the morphology of as-synthesized SnS powders can be tuned from plate into belt shapes with reduction in the amount of NaOH. After sintering, the pellets sintered from larger SnS belts showed strengthened anisotropy due to texturing effect compared with those sintered from SnS plates, and led to enhanced electrical performance along the in-plane direction ({111}-preferred). The tuned reaction condition with reduction in the amount of NaOH also increased the Sn vacancies, leading to reduced band gap, shifted Fermi level, and subsequently enhanced hole concentration. Consequently, the overall thermoelectric performance was enhanced with reducing the amount of NaOH. This study indicates texture engineering is effective in tuning anisotropy of polycrystalline SnS, enhancing the thermoelectric performance, and can be realized via morphology engineering.