Photo-absorption properties of van der Waals heterostructure of monolayer InSe with silicene, germanene and antimonene

Abstract In this work, we study van der Waals (vdW) heterostructures consisting of the emerging photonic material, 2-dimensional (2D) InSe, with the lattice-matched 2D materials silicene, germanene and antimonene, using ab-initio simulations. We employ density functional theory (DFT) to calculate the structural and electronic properties of the vdW hetero-bilayers. The optical spectra of the systems are evaluated by solving the Bethe-Salpeter equation (BSE) on top of the GW quasiparticle bands. A strong response in the IR-visible region of the optical spectra is seen in case of InSe-Si and InSe-Ge vdW lattice whereas the InSe-Sb structure shows better performance in the visible-UV region, with better prospect of excitonic charge separation. A good absorbance in the IR-visible and the visible-UV region, can be achieved with these structures with computed theoretical photocurrent densities significantly larger than conventional photovoltaic materials. While individually the vdW structures can be useful in photonic applications, the complimentary nature of absorption with InSe-Sb and InSe-Si/Ge structures can also be utilized in multi-junction heterostructure solar cells.