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

Abstract

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)2PbI4 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.