A promising thermoelectrics In4SnSe4 with a wide bandgap and cubic structure composited by layered SnSe and In4Se3

The wide-bandgap cubic-structure semiconductor In4SnSe4 can be regarded as a product of compositing two typical layered thermoelectric materials SnSe and In4Se3. Remarkably, In4SnSe4 inherited low thermal conductivity from its parent materials. To advance the potential thermoelectric property of In4SnSe4, we systematically investigated its crystal structure and the origin of the intrinsic low thermal conductivity. In4SnSe4 crystallized in a cubic phase (space group Pa3¯), with the lattice parameters of a = b = c = 12.66 Å. The anisotropy of InSe bonds in the lattice determined the complex structure of In4SnSe4 with 72 atoms in the primitive cell. More importantly, sound velocity and elastic properties unclosed the strong anharmonicity in In4SnSe4, which contributed greatly to the low thermal conductivity. With first-principles calculations, it was found that the lone-pair electrons from In+ mainly caused the anharmonicity in the lattice. Additionally, Br was proved to be an effective dopant for In4SnSe4 to improve the electrical transport properties. This work indicated that the complex wide-bandgap semiconductor In4SnSe4 with cubic phase and intrinsic low thermal conductivity was a new promising thermoelectric material with appropriate doping.