First principles study for band engineering of MoS₂ monolayer with Mn doping

The electronic properties of MoS₂ monolayer with various levels of Mn incorporation are investigated using the Heyd-Scuseria-Enrzerhof hybrid functional. Four Mn doping concentrations are considered: 2.78%, 6.25%, 11% and 25%. Results show that, with the increasing Mn doping, the Mn-induced intermediate band (IB) ranges from the localized to dispersive states, effectively acting as a stepping stone to help relay valence electrons to the conduction band. Simultaneously, the IB divides the band gap into narrower subgaps, inducing significant band-gap reduction. The combined effects of the IB widening and the band-gap narrowing engineer the band structure to extend the optical absorption of MoS₂ monolayer into the long-wavelength region of solar irradiance. Detailed formation-energy calculations reveal a high favorability for Mn to substitute Mo in MoS₂ monolayer under the Mo-poor condition. This work provides a fundamental guidance for broadening the functional applications of MoS₂ monolayer in photocatalysis, photovoltaic cells and other photonic devices.