Optoelectronic and photocatalytic behaviour of a type-II GaAlS2/HfS2 heterostructure: ab initio study

Abstract

Theoretical examination based on first principle computation has been conducted for van der Waals heterostructure (vdwHS) GaAlS2/HfS2 including structural, optoelectronic and photocatalytic characteristics. From the adhesion energy calculation, the AB configuration of GaAlS2/HfS2 vdwHS is the most stable. A type-II GaAlS2/HfS2 vdwHS is a dynamically and thermally stable structure. The band edge position, projected band, and projected charge densities verify the type-II alignment of GaAlS2/HfS2 vdwHS. For GaAlS2/HfS2, GaAlS2 is acting as a donor and HfS2 is acting as an acceptor ensured by the charge density difference plot. The electron localized function validates the weak van der Waals interaction between GaAlS2 and HfS2. The GaAlS2/HfS2 vdwHS possess an indirect bandgap of 1.54 eV with notable absorption in the visible range. The findings assure that the GaAlS2/HfS2 vdwHS is an efficient photocatalyst for pH 4–8. The band alignment of GaAlS2/HfS2 is suitable for Z-scheme charge transfer. The strain influenced band edge suggests that the GaAlS2/HfS2 vdwHS remains photocatalytic for strain −4% to +6% in both cases of uniaxial and biaxial strains.