Electronic and optical properties of MoS2 (0 0 0 1) thin films: Feasibility for solar cells

Electronic and optical properties with different thicknesses of MoS2 thin films (1–14 layers) have been computed using full potential linearized augmented plane wave method. In addition, to study the quantum size effect in MoS2 thin films for different thicknesses, the surface energies and the work functions have also been calculated. It is observed that the quantum size effect is present upto 6 layers in the MoS2 thin films. Monolayer of MoS2 thin film shows a direct band gap of 1.84 eV, while the indirect band gap is larger in MoS2 thin film with 2 layers when compared to that in the bulk MoS2. An increase in the number of layers (2 L → 14 L) reduces the indirect band gap significantly. It is also observed that the dielectric constants and the absorption coefficients increase with the thickness of the thin films and these values for 8 or higher numbers of layers are comparable with the bulk material values, suggesting that a film of 8 layers (thickness ≈ 49 Å) of MoS2 is sufficient for economical fabrication of solar cells. Anisotropies in refractive indices in bulk and thin film forms are also discussed.