The optical properties of few-layer MoS 2 by DFT calculations

In this work, the electric and optical properties of few layer MoS 2 were systematically investigated theoretically and experimentally, especially monolayer and bilayer. Firstly, the effects of different pseudopotentials on the calculation results of MoS 2 have been investigated. It indicates that the normal-conserving pseudopotential is suitable for accurate calculations of the electronic properties. Then, for deep understanding of the photoluminescence mechanism of MoS 2, the electronic structure and optical properties of MoS 2 were calculated by first-principles calculations with normal-conserving pseudopotential. The density of states of bilayer MoS 2 at the Fermi level is higher than that of monolayer MoS 2, indicating that bilayer MoS 2 has a larger carrier density. Comparing the optical properties of monolayer and bilayer MoS 2, it can be concluded that along the C-axis direction, bilayer MoS 2 exhibits higher absorption in the wavelength range of 496–1240 nm, while the monolayer one has a remarkable absorption below 496 nm. These findings indicate that bilayer MoS 2 preferentially absorbs visible and near-infrared light, while monolayer MoS 2 tends to absorb ultraviolet light. These explained the different absorption characteristics of monolayer and bilayer MoS 2 and give guidance for selecting the thickness of MoS 2 material in applications of optoelectronic devices.