Organic Cation Modulation of Interlayer Exciton Emission in Two‐Dimensional Perovskite/Monolayer Transition Metal Dichalcogenide Heterostructures

Abstract Interlayer excitons (IXs) are demonstrated in two‐dimensional (2D) perovskite/transition‐metal dichalcogenide (TMD) heterostructures regardless of the lattice match, momentum mismatch, and thermal annealing processes. The broad selection of 2D perovskites and TMDs together with the robust interlayer coupling between constituent layers make 2D perovskite/TMD heterostructures an attractive platform for studying IXs. However, studies on IXs in 2D perovskite/TMD heterostructures are still in their infancy, and how the organic cation affects the IXs in 2D perovskite/TMD heterostructures remains elusive. Herein, this article reports on IXs emission from heterostructures consisting of monolayer WSe 2 and 2D perovskites with different organic cations. Notably, by temperature‐dependent photoluminescence studies on (EA) 2 PbI 4 /WSe 2 and (PEA) 2 PbI 4 /WSe 2 heterostructures (EA = ethylamine and PEA = phenylethylammonium), it is found that the organic cations of 2D perovskites can effectively change the exciton binding energy of the IXs and thus the emission peak of the IXs. The observed difference can be ascribed to the significant dielectric constant difference between their organic cations. Furthermore, the change in the organic cations can also affect the dipole–dipole interaction and lifetime of IXs. The findings provide critical insights into the 2D perovskite/TMD heterointerfaces and also open up new opportunities for exploiting tunable exciton devices based on IXs.