Band edge states dominated by interface atoms and strong interlayer coupling work together to drive the direct generation of interlayer excitons in vdW heterostructures

Previous generation of interlayer excitons has been limited to heterojunctions of transition-metal dichalcogenides, where excitons form via a two-step process of intralayer excitation followed by interlayer transfer. Herein, we find a series of materials that exhibit efficient one-step generation of interlayer excitons. In type-II systems where band edge states originate from interface atoms, the interlayer coupling maximizes orbital overlap, this distinct feature dramatically enhances the interlayer transition probability. By investigating 57 composite heterostructures composed of polar X2Y3 (X = Al, Ga, and In; Y = S, Se, and Te) and group-VA (As, Sb, and Bi) monolayers, we successfully screened 20 ideal configurations. These configurations exhibit an exceptionally high interlayer transition probability to one-step generate interlayer excitons. This finding deepens the understanding of interlayer exciton formation mechanisms in 2D van der Waals heterostructures.