III-VI van der Waals heterostructures for sustainable energy related applications.

van der Waals (vdW) heterostructures, achieved by binding various two-dimensional (2D) materials together via vdW interaction, expand the family of 2D materials and show fascinating possibilities. In this work, we have systematically investigated the geometrical structures, electronic structures, and optical properties of III-VI (MX, M = Ga, In and X = S, Se, Te) vdW heterostructures and their corresponding applications in sustainable energy related areas based on first principles calculations. It is highlighted that different heterostructure types can be achieved in spite of the similar electronic structures of MX monolayers. Meanwhile, the potential applications of the heterostructures for sustainable energy related areas have been further unraveled. For instance, type-II InS/GaSe and GaS/GaSe vdW heterostructures can separately produce hydrogen and oxygen at the opposite parts. On the other hand, a type-II GaSe/GaTe heterostructure with a direct band gap compatible with silicon has been proposed to be a potential solar cell material with a power conversion efficiency over 18%. Furthermore, a gapless type-IV semi-metallic InTe/GaS heterostructure has been predicted to be a Li-ion battery anode material based on three-step lithiated analysis. The present results will shed light on the sustainable energy applications of such remarkable artificial MX vdW heterostructures in the future.