  A GW calculation based on a truncated coulomb interaction with an added small
q limit was applied to 2D van der Waals hetro-layered structures, and the Kane
dispersion model was used to determine the accurate band gap edge. All ab
initio calculations were performed with the gpaw package. Our findings show
that layering the same or different types of atoms with a vacuum in between has
an enormous impact on band alignment, effective mass of holes and electrons,
exciton binding energy, thermoelectric characteristics, density of hot
electrons, and electronic band gaps.Thus, layered interactions of the same kind
constrain the configuration to have a direct band gap, whereas different kinds
allow for an indirect gap, resulting in an indirect exciton with a greater
binding energy due to the band confinement effect. Furthermore, the
hetrostructure of the highest configuration facilitates the relaxation of hot
electrons by forming unoccupied states. This leads to a high density of hot
electrons dispersing over unoccupied states, which lessens their sensitivity to
temperature; in other words, thermal drop prolongs electron-hole pairing.
$\mathrm{MoSe_{2}-MoS_{2}}$ and $\mathrm{MoSeSe-MoSSe}$ have an improved
seebeck coefficient among the various possible configurations because of their
low heat conductivity, ability to produce a higher density of states and empty
states, improved optical gap, and multiple excitation peaks that resemble the
experimental photoluminescence spectrum.
