Site-controlled interlayer coupling in WSe2/2D perovskite heterostructure

Interlayer excitons (IXs) formed in transition metal dichalcogenides (TMDs)/two-dimensional (2D) perovskite heterostructures are emerging as new platforms in the research of excitons. Compared with IXs in TMD van der Waals heterostructures, IXs can be robustly formed in TMDs/ 2D perovskite heterostructures regardless of the twist angle and thermal annealing process. Efficient control of interlayer coupling is essential for realizing their functionalities and enhancing their performances. Nevertheless, the study on the control of interlayer coupling strength between TMD and 2D perovskites is elusive. Therefore, we realize the control of interlayer coupling between monolayer WSe2 and (iso-BA)(2)PbI4 with SiO2 pillars in situ. An abnormal 10-nm blue shift and 2.5 times photoluminescence intensity enhancement were observed for heterostructures on the pillar, which was contrary to the red shift observed in TMD heterobilayers. We attributed the abnormal blue shift to the enhanced interlayer coupling arising from the reduced gap between constituent layers. In addition, IXs became more dominant over intralayer excitons with enhanced coupling. The interlayer coupling could be further engineered by tuning the height (h) and diameter (d) of pillars. In particular, an additional triplet IX showed up for the pillar with an h/d ratio of 0.6 due to the symmetry breaking of monolayer WSe2. The symmetry breaking also induced an anisotropic response of IXs. Our study is beneficial for tuning and enhancing the performance of IX-based devices, exciton localization and quantum emitters.

Automated summary

Recently, it has been discovered that interlayer excitons can be robustly formed in transition metal dichalcogenides/two-dimensional perovskite heterostructures, and their performance can be enhanced by controlling the interlayer coupling. By tuning the height and diameter of pillars, the interlayer coupling can be further engineered. Additionally, the symmetry breaking of monolayer WSe2 can lead to the appearance of an additional triplet interlayer exciton and induce an anisotropic response.