Switchable band alignment in 2D-perovskite/WS ₂ heterostructures for tunable exciton transport and valley polarization

Abstract Van der Waals heterostructures integrated by two-dimensional (2D) transition metal dichalcogenides (TMDs) hold great potential for engineering promising exciton phenomena, particularly interlayer excitons (IXs) featuring extended lifetimes and permanent out-of-plane electric dipole moments. While electrically controllable IX emission has been extensively explored in TMD heterobilayers, reconfiguring their band alignment to achieve selected exciton states and exploit these states for novel excitonic functionalities remains an urgent challenge. Here, we demonstrate dynamic exciton control by electrically tunable band alignment transitions between type-II and type-I configurations in WS 2 /(iso-BA) 2 PbI 4 heterostructures, enabling reversible conversion between charged interlayer (IX⁻) and charged intralayer (X⁻) excitons. By tailoring these exciton states, we achieve two critical functionalities: (i) 7 μm ON/OFF control of exciton transport via transition between delocalized IX⁻ (ON) and confined X⁻ (OFF) states; (ii) Valley polarization switching with a 16.3 ON/OFF ratio, leveraging distinct spin-valley configurations of IX⁻ (unpolarized) and X⁻ (polarized). Unlike twist-angle-dependent TMD heterobilayers, this platform operates independently of stacking alignment, establishing a broadly hybrid 2D system as a practical paradigm towards programmable nanophotonic circuits.