Density functional study of Na doped Tin selenide

Tin selenide (SnSe) has attracted the attention of scientific community since it has been discovered positing a record high figure of merit (ZT) of 2.6 at 923 K in single crystal. However SnSe lacks performances when it comes to its polycrystalline counterpart due to low electrical conductivity of 10−3 S m−1. Here we present a first principle comparative study of pristine SnSe and Na doped (6.25 atomic %) SnSe to look in depth to the band structure and density of states modification due to doping. Our findings reveal that pure SnSe has an indirect band gap of 0.737 eV, while the doped sample has an indirect band gap of 0.687 eV. SnSe shows multiple band extremas in both valance and conduction bands within the range of carrier thermal energy, however in doped samples multiple extremas occurs only in valance bands. The doped sample shows a relatively broader valance band maxima and higher density of states near the Fermi level (EF) in contrast to the pristine SnSe, which corroborates this to be a potential candidate for thermoelectric applications.