Temperature- and voltage-dependent photoluminescence of interlayer excitons in MoS₂/WS₂/MoS₂ trilayer heterostructures

When monolayers of two-dimensional transition metal dichalcogenides (TMDs) are vertically stacked to form van der Waals heterostructures, interlayer charge transfer occurs, resulting in interlayer excitons (ILEs) that are spatially separated yet Coulomb-bound. Compared to bilayer heterostructures, trilayer configurations introduce a dual-interface coupling, whose Stark response transitions from a linear behavior to a non-monotonic one (quadratic at low fields and linear at high fields). However, relevant experimental studies remain limited to date. This work focuses on two types of trilayer van der Waals heterostructures (MoS₂/WS₂/MoS₂ and WS₂/MoS₂/WS₂), primarily regulating both structures through electric and optical fields. Temperature-dependent photoluminescence spectroscopy measurements reveal the suppression of ILEs on the intrinsic emission of each layer. Meanwhile, ILE emission peaks in the heterostructures shows that with decreasing temperature, the two ILE sub-peaks exhibit distinct variation trends. On the other hand, continuous electric field regulation of ILEs in the trilayer heterostructures reveals that the peak positions of the two ILE sub-peaks exhibit an asymmetric redshift under both positive and negative voltages, distinct from the conventional Stark shift observed in bilayer systems. This study uncovers the independent regulatory mechanisms of stacking order and vertical electric field on the energy, oscillator strength, and charge state of ILEs in trilayer TMD heterostructures, providing experimental support for the construction of tunable multilayer excitonic optoelectronic devices.