First principles GW-Bethe Salpeter equation excitonic spectrum of van der Waals heterostructure: The case of PtS2-SnS2 heterostructure

The accurate determination of light absorption in the material is necessary to understand the photocatalytic mechanism. Here, we present the systematic study of light absorption in the prototypical Van derWaals (vdW) heterostructure PtS2-SnS2 by including the electron-hole interaction in the computational calculation by the GW Bethe Salpeter Equation (GW-BSE) approach. The GGA-PBE level bandgap of the PtS2 -SnS2 vdW heterostructure is calculated to be 1.09 eV which is less than that of monolayers of PtS2 and SnS2. Later, GW-BSE absorption spectra pointed out the bound excitonic peaks of PtS2-SnS2 vdW heterostructure which have significant impact on the light absorption property of the material. The first excitonic peak of this vdW heterostructure obtained at the 2.17 eV which is in the low energy range compared to monolayers of PtS2 and SnS2. This low energy shift of the first excitonic peak will be favourable for better light absorption as well as boosted photoconversion efficiency of the PtS2-SnS2 vdW heterostructure.