Effect of vertical strain and in-plane biaxial strain on type-II MoSi2N4/Cs3Bi2I9 van der Waals heterostructure

Abstract

Construction of van der Waals heterostructures (vdWHs) from layered materials may form new types of optoelectronic devices with better performance compared to individual layers. Here, we investigate theoretically the structural stability, electronic properties, charge-transport mechanisms, and optical properties of two-dimensional (2D) MoSi2N4/Cs3Bi2I9 vdWHs by using the first-principles calculations. Our results demonstrate that the 2D MoSi2N4/Cs3Bi2I9 vdWHs possess a direct bandgap and type-II band alignment due to the built-in electric field induced by the electron transfer from MoSi2N4 to Cs3Bi2I9 layer, which can prevent photoinduced electrons and holes from recombination and thus enhance the carrier lifetime. Furthermore, the optical absorption of the heterostructure is enhanced in the visible and ultraviolet region, and its electronic property is tunable under in-plane strains with a clear metal–semiconductor transition. Finally, we explore more A3B2X9/MA2Z4 vdWHs with A = Cs; B = In, Sb, Bi; and X = Cl, Br, I in A3B2X9 and M = Cr, Mo, Ti; A = Si; and Z = N, P in MA2Z4, and we find all three types of band alignments (type-I, type-II, and type-III). Our study provides a comprehensive theoretical understanding of the electronic and optical properties of perovskite-based heterostructures and indicates its potential applications in optoelectronic devices.