Optoelectronic, mechanical, and thermoelectric properties of Na/I co-doped SnSe via ab initio calculations

Tin selenide-based materials have attracted much attention recently because of their unique properties. This study investigates the effect of Sodium and Iodine co-doping on the optoelectronic, mechanical, and thermoelectric properties of orthorhombic SnSe via First-principles calculations. Na/I co-doped crystal was found to have a triclinic structure, and its electronic bandgap is 0.325 ​eV, whereas the calculated band gap of the pristine SnSe is 0.824 ​eV using SCAN functional. Na/I co-doping alters the Fermi level of SnSe up to its conduction bands, resulting in an n-type system. Furthermore, the static dielectric constant shows that the doped system could be suitable for capacitors and solar cell applications. According to the calculated elastic constants, the doped system is stable. Moreover, it has a negative Poisson's ratio value suggesting it's auxetic sensor material. The thermoelectric performance is examined from 300 ​K to 800 ​K across a broad range of carrier concentrations for the doped and undoped SnSe systems. We have found that Na/I co-doping enhances the electrical conductivity and the Seebeck coefficient of SnSe. The highest power factor calculated for the doped system was 27.9μV/Kcm at carrier concentration of n≅−3×10²⁰cm⁻³.