Observation of interlayer excitons in trilayer type-II transition metal dichalcogenide heterostructures

Vertically stacked transition metal dichalcogenide (TMD) heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional limit. In such structures, spatially indirect interlayer excitons (IXs) can be generated in adjacent layers because of strong Coulomb interactions. However, due to the complexity of the multilayered heterostructure (HS), the capture and study of the IXs in trilayer type-II HSs have so far remained elusive. Here, we present the observation of the IXs in trilayer type-II staggered band alignment of MoS₂/MoSe₂/WSe₂ van der Waals (vdW) HSs by photoluminescence (PL) spectroscopy. The central energy of IX is 1.33 eV, and the energy difference between the extracted double peaks is 23 meV. We confirmed the origin of IX through PL properties and calculations by the density functional theory, we also studied the dependence of the IX emission peak on laser power and temperature. Furthermore, the polarization-resolved PL spectra of HS were also investigated, and the maximum polarizability of the emission peak of WSe₂ reached 11.40% at 6 K. Our findings offer opportunities for the study of new physical properties of excitons in TMD HSs and therefore are valuable for exploring the potential applications of TMDs in optoelectronic devices.