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 In[sbnd]Se 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.