Reconfigurable band alignment of m−GaS/n−XTe2 ( X=Mo , W) multilayer van der Waals …

Integrating two-dimensional materials into van der Waals heterostructures (vdWHs) is considered to be an efficient strategy for multifunctional devices. Here, the $m\text{\ensuremath{-}}\mathrm{GaS}/n\text{\ensuremath{-}}{\mathrm{MoTe}}_{2}$ (${\mathrm{WTe}}_{2}$) multilayer vdWHs are designed to explore possible characteristics through engineering the electric field, strain, and layer combination m/n. For the most stable $\mathrm{GaS}/{\mathrm{MoTe}}_{2}$ (${\mathrm{WTe}}_{2}$) bilayer vdWHs obtained by global search with direct band structure and straddling gap, the proper compression strain and positive electric field regulates the band structure from straddling gap to staggered case. Particularly, the $m\text{\ensuremath{-}}\mathrm{GaS}/n\text{\ensuremath{-}}{\mathrm{WTe}}_{2}$ multilayer vdWHs have the straddling band alignment when the layer number of GaS is 1L $(m=1)$, while it can be transferred to staggered case with the $m>1$ due to the quantum confinement effect. In addition, the $\mathrm{GaS}/{\mathrm{MoTe}}_{2}$ vdWHs can be used as highly efficient solar cells with power conversion efficiency up to 27%. Also, the photoresponsivity and external quantum effects are increased from 0.048 (8%) to 0.18 A/W (42%) for the multilayer vdWHs. These results indicate that the $m\text{\ensuremath{-}}\mathrm{GaS}/n\text{\ensuremath{-}}{\mathrm{MoTe}}_{2}$ (${\mathrm{WTe}}_{2}$) multilayer vdWHs can be taken as reconfigurable system in highly efficient solar cells and photodetectors.