Bandgap tuning in MoSSe bilayers: synergistic effects of dipole moment and interlayer distance

From first principles calculations, the lowest energy structures of bilayer MoSSe with different combination patterns (S-S, Se-Se, and S-Se bilayers) have been confirmed. The results demonstrate that the band gap of bilayer MoSSe can be tuned by interlayer distance and dipole moment. A larger interlayer distance increases the band gap, while a larger dipole moment reduces the band gap. That is, the gap is affected by the synergistic effects of dipole moment and interlayer distance in a MoSSe bilayer. Our results provide a new way to realize band gap modulation by changing the dipole moment or the interlayer distance. Impressively, another important finding is that the S-Se bilayer has a type-II band alignment, which makes it a good candidate for applications in optoelectronics.