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

• We explored a way of improving TE properties of 2H-MoQ2 on DFT methods.
• The mixed-layer compounds MoS2/MoSe2 have enhanced thermoelectric properties.
• This is caused by modulated electronic structure of mixed layer compound.
• Layer mixing approach should be regarded as a useful way to improve TE properties.

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 MoQ2, the band gap size could be adjusted in mixed-layer compound MoS2/MoSe2. Also, the indirect band gap in pure MoQ2 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.

On the basis of density functional calculations we predict that the mixed-layer compounds 2H-MoS2/2H-MoSe2, in which two different layers 2H-MoS2 and 2H-MoSe2, have enhanced thermoelectric properties because of the increased density of states around the Fermi level and the decreased band gap size. Figure optionsDownload as PowerPoint slide