Photoluminescence\nBehaviors of 2D-Cs<sub>3</sub>Bi<sub>2</sub>I<sub>9</sub>/2D-MoS<sub>2</sub> Vertical Heterostructures\nPrepared by the One-Step CVT Growth Method

Two-dimensional (2D) perovskites are emerging materials\nwith large\nexciton binding energy, tunable bandgap, and layered properties. The\nweak van der Waals (vdW) coupling between the layers in 2D perovskites\nis easy to integrate with other layered materials, such as graphene\nand transition metal dichalcogenides, forming heterostructures (HS)\nto expand their functions. In order to obtain excellent HS materials,\nit is necessary to develop high-quality and low-cost, scalable preparation\nmethods for 2D HS. Notably, chemical vapor transport (CVT) is a powerful\nmethod that may meet the above requirements. Herein, we first synthesized\nthe HS of 2D-Cs<sub>3</sub>Bi<sub>2</sub>I<sub>9</sub>/2D-MoS<sub>2</sub> using the one-step CVT method, then characterized its structure\nand properties, and further elucidated the underlying mechanism of\nphotoluminescence behavior. It has been proven that this is a type\nII band alignment HS material combined with theoretical calculations.\nThen, we used a femtosecond pump measurement to study the photodynamic\nprocess of the HS and reveal the energy transfer and charge transfer\nin the HS, which also provides a foundation for future HS device fabrication.