Density functional theory investigation of the electronic structure and thermoelectric properties of layered MoS₂, MoSe₂ and their mixed-layer compound

First principles density functional theory calculations were carried out for the 2H-MoQ₂ (Q=S and Se) and their hypothetical mixed-layer compound. Due to the different electronegativities of S and Se atoms on MoQ ₂, the band gap size could be adjusted in mixed-layer compound MoS₂/MoSe₂. Also, the indirect band gap in pure MoQ ₂ compounds is changed to the pseudo direct band gap in mixed-layer MoS₂/MoSe₂ which is similar to the monolayer compound. The layer mixing enhances the thermoelectric properties because of the increased density of states around the Fermi level and the decreased band gap size. Therefore, we suggest that this layer mixing approach should be regarded as a useful way to modulate their electronic structures and to improve their thermoelectric properties.