Optoelectronic, mechanical, and thermoelectric properties of Na/I co-doped SnSe using density functional theory

Tin selenide-based materials have attracted a lot of attention recently because of their unique properties. This study investigates the effect of Sodium and Iodine co-doping on the electronic, optical, mechanical, and thermoelectric properties of orthorhombic SnSe crystal based on First-principles density functional theory. As a result of our findings, the doped system is a potential candidate for a wide variety of applications. Na/I co-doped crystal was found to have a P1 triclinic structure, and its electronic bandgap is 0.53 eV, whereas the calculated band gap of the pristine SnSe is 1.08 eV using the Hybrid functional (HSE06). 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, which indicates that it is an auxetic material that can be used in sensor technology. The thermoelectric performance is examined from 300K to 800K 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 micro V/Kcm at carrier concentration of n= -3e20 cm^-3.