Thickness dependence of solar cell efficiency in transition metal dichalcogenides MX2 (M: Mo, W; X: S, Se, Te)

Bulk transition metal dichalcogenides are indirect gap semiconductors with optical gaps in the range of 0.7-1.6 eV, which makes them suitable for solar cell applications. In this work, we study the electronic structure, optical properties, and the thickness dependence of the solar cell efficiencies of MX2 (M: Mo, W; X: S, Se, Te) with density functional theory and GW + BSE. Through this analysis, we find a change in solar cell efficiency trends at slab thicknesses of 3 mu m. For thin films solar cells (thicknesses smaller than 3 mu m), the tellurides present the highest efficiencies (about 20% for a 100 nm thick slab). In contrast, for thicknesses greater than 3 mu m, our results indicate that a maximum solar cell efficiency can be achieved in WS2. For instance, a 100 mu m slab of WS2 presents a solar cell efficiency of 36.3%, making this material a promising candidate for solar cell applications.