Effect of lattice defects on electronic structure and thermoelectric properties of 2D monolayer MoS2

Molybdenum disulfide (MoS2) is considered as a promising economical and non-toxic thermoelectric material due to its low thermal conductivity and high Seebeck coefficient. However, its power factor is not ideal, which limits its energy conversion efficiency in thermoelectric applications. In this paper, the electronic structure of pure and lattice-defect MoS2 2D monolayer is studied by using the first principles method and non-equilibrium Green's function (DFT-NEGF). The effects of atom substitution and vacancy defect on the thermoelectric properties of MoS2 2D monolayer are also investigated. The result shows that the S-vacancy changes the bandgap by introducing donor and acceptor levels, while the substitution of Se and Te atoms slightly increases the bandgap value. In the case of n-type doping, the ZT value of the S atom substituted MoS2 reaches 1.19 at 300 K, while the Te atom substitution MoS2 has a higher ZT value of almost 2.26 at 800 K. The analysis shows that the thermal conductivity of MoS2 decreases due to the presence of S-vacancy, while the atomic substitution of Se and Te increases the power factor of MoS2. This work may provide a new method and theoretical guidance for achieving high performance of thermoelectric devices in the energy industry. •The S-vacancy changes the bandgap of monolayer MoS2 by introducing donor and acceptor levels.•For n-type defect system, the maximum ZT value of S-vacancy structure is 1.19 and Te substitution doping system is 1.01.•Thermal conductivity of MoS2 is reduced due to the S-vacancy, while the Se and Te atomic substitution increases the power factor of MoS2.