Strain tuned InSe/MoS bilayer van der Waals heterostructures for photovoltaics or photocatalysis.

The isolation of different two-dimensional materials and the possibility to combine them in vertical stacks have led to new material systems, namely heterostructures based on two-dimensional crystals. By using density functional theory, we found that the InSe/MoS2 bilayer shows an indirect band gap of 0.65 eV with optical absorption over a wide range (300-800 nm) and a preferable separation of photogenerated electron-hole pairs. Moreover, the band gap can be readily tuned by external strain engineering, leading to a transition from the indirect band gap to a direct band gap of 1.55 eV under 7% compressive strain, where there is an enhanced and continuous spectrum. In addition, under a tensile strain of 9%, the bilayer is metallic. All of these properties enable the development of excellent photoelectric devices from the heterostructures with strain engineering.