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.

(a) Absorption coefficients and (b) imaginary part of dielectric functions for bulk MoS2 and different layers (L) of MoS2 (0 0 0 1) for perpendicular (left panel) and parallel (right panel) directions of polarization (E⊥z and E||z). The z-axis is considered as the optical axis. In the inset of left panel of figure (a), the absorption coefficients for 14 L MoS2 film using LDA and GGA schemes are also shown.Figure optionsDownload as PowerPoint slideHighlights
• Deals electronic and optical properties of MoS2 (0 0 0 1) films using FP-LAPW method.
• Surface energies and work functions are computed for 2–14 monolayers (L).
• Indirect band gap decreases with the increase in film thickness (2 L → 14 L).
• Presented peculiar trends of dielectric constants and absorption coefficients.
• Optical data suggest solar cell fabrication using 8 L of MoS2 (0 0 0 1).