Tailoring the optoelectronic properties and dielectric profiles of few-layer S-doped MoO3 and O-doped MoS2 nanosheets: a first-principles study

To gain insights into few layer (FL) van der Waals MoO3-xSx/MoS2-O-x(x) heterostructures for photocatalytic applications, we analyze how the concentration (x) and location of anionic isovalent atom (S or O) substitutions impact their opto-electronic properties and high frequency dielectric constant profiles. By using density functional theory (DFT) calculations within the HSE06 functional, we show that the electronic band gap of FL MoO3-xSx decreases with increasing x, while the dielectric constant profile and absorption coefficient in the UV-vis range increase. The stronger band gap reductions are obtained when S-atoms are located in the internal bulk region of FL MoO3-xSx and in interaction with O-atoms of the neighboring layer. Moreover, the conduction and valence band (CBNB) levels are shifted to higher energy values in the case of the edge location (external surface) of these S-atoms. Thanks to the determination of the thermodynamic diagrams of 4L MoO3-xSx and 6L MoS2-xOx, we propose optimal heterojunctions made of 4L MoO3-xSx with either single-layer (SL) or FL MoS2 with CB/VB levels compatible with a Z-scheme working principle and with potentials required for photocatalysis applications such as the photolysis of water into O-2 and H-2. This study combined with our previous theoretical investigations on bulk materials and SL provides a thorough analysis of SL-FL MoO3-xSx/MoS2 heterojunctions where the concentration and location of S-atoms in MoO3-xSx are key to design efficient materials for water photolysis.

Automated summary

By using density functional theory, the opto-electronic properties and high frequency dielectric constant profiles of few layer MoO3-xSx/MoS2 heterostructures have been investigated. It is found that the electronic band gap decreases and the dielectric constant increases with increasing S concentration in FL MoO3-xSx. The band gap reduction is more significant when S atoms are located in the internal bulk region, and the conduction and valence band levels shift to higher energy at the edge location.