Aliovalent Doping and Texture Engineering Facilitating High Thermoelectric Figure of Merit of SnSe Prepared by Low-Temperature Hydrothermal Synthesis

The IV-VI compound SnSe is an environmentally friendly and high-performance thermoelectric material with intrinsically low lattice thermal conductivity. Recent research efforts have focused on enhancing carrier concentration and effective mass to improve power factors, thereby achieving superior thermoelectric performance as reflected in the figure of merit ZT. In context of the anisotropic crystal structure of SnSe, this study utilized a hydrothermal method to synthesize Rb-doped SnSe nanosheets. Rb acts as an acceptor dopant, increasing the hole concentration to 2.0 x 1019 cm-3 and promoting second valence band participation in transport at room temperature, significantly elevating the ZT value of polycrystalline SnSe to 1.41 at 773 K. Furthermore, texture engineering was implemented through a secondary sintering process. This approach facilitates the organized stacking of grains with highly preferred orientations, resulting in a notable improvement of hole mobility perpendicular to the pressure direction to further increase the power factor. By synergistically combining carrier concentration optimization with texture engineering strategies, an exceptional ZT value of 1.74 at 773 K was achieved in polycrystalline SnSe. This work presents a cost-effective, straightforward, and low-temperature synthesis route for the large-scale production of high-performance SnSe thermoelectric materials, offering significant potential for practical applications in energy harvesting and conversion.