Enhanced absorption in SnS/SnSe, SnS/ZnS, and SnS/ZnSe vdW heterostructures for optoelectronic applications: DFT insights

Abstract

The electronic and optical properties of monolayers of tin monochalcogenides and zinc monochalcogenides are elucidated by utilizing density functional theory. The calculated results indicate that the monolayers of tin monochalcogenides (SnS and SnSe) have low bandgap and significant absorption in some segments of the visible region (~400 nm to ~500 nm). However, the monolayers of zinc monochalcogenides (ZnS and ZnSe) have wide bandgap and negligible absorption in the visible region, which limits their optical performance. Despite low absorption in visible region, ZnS and ZnSe exhibit fascinating properties such as wide band gap, cheapness, low toxicity, earth abundance, structural stability, and high refractive index. To identify the combined potential of zinc and tin, the van der Waals heterostructures SnS/SnSe, SnS/ZnS, and SnS/ZnSe are formed, and their optical and electronic properties are calculated. The calculated results illustrate that the formed heterostructures exhibit bandgap lowering and enhanced visible light absorption. The optical absorption is entirely shifted towards the visible region due to the formation of heterostructure (redshift). The enhanced visible light absorption and narrowed bandgap of the formed heterostructures make them a potential candidate for the fabrication of optoelectronic devices and solar cells.