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abstract

 The recently synthesized GaS and MoSe2 nanosheets have been used as appropriate substrates for other layered materials, e.g. silicene/GaS heterosheets akin to graphene/BN systems. Here, we have performed a comprehensive first-principles study of the electronic and optical properties of two-dimensional (2D) GaS/MoSe2 hetero-bilayers based on density functional theory (DFT). We found almost all proposed GaS/MoSe2 hetero-bilayers in the current study have an indirect band gap from the point to the K point, except for one with a direct band gap at the K point. Tunable band gaps GaS/MoSe2 hetero-bilayers can be controlled by strain modulation. State-of-the-art GW-Bethe–Salpeter method, accounting for electronelectron and electron-hole interactions, has been employed to compute accurate absorbance spectra for layered materials. Compared with its composing GaS and MoSe2 monolayers, GaS/MoSe2 heterobilayers show superior behavior on optical absorbance, indicating a stronger visible-light absorption and applications in solar energy harvesting. We foresee that the novel GaS/MoSe2 hetero-bilayers would stimulate the fabrication of materials with unprecedented optical and physico-chemical properties that may apply in nanodevices and photovoltaic cells.

4. Conclusion

In summary, we have investigated the electronic and optical properties of various GaS/MoSe2 hetero-bilayers by DFT and stateof-the-art many-body perturbation theory including quasiparticle GW approach and BSE. Even though GaS monolayer has a distinct electronic property from MoSe2 monolayer, they have the same symmetry with close lattice constants, making them good candidates to form GaS/MoSe2 hetero-bilayers. Most GaS/MoSe2 hetero-bilayers in our current study have an indirect band gap from the point to the K point. With respect to the optical absorbance, GaS/MoSe2 hetero-bilayers show superior behavior compared with its composing GaS and MoSe2 monolayers. These theoretical predictions suggest that GaS/MoSe2 hetero-bilayers might be very promising for optoelectronic applications at the nanometer scale.