Enhanced Trion Emission in Monolayer MoSe₂ by Constructing a Type‐I Van Der Waals Heterostructure

Abstract

Abstract Trions, quasi‐particles consisting of two electrons combined with one hole or of two holes with one electron, have recently been observed in transition metal dichalcogenides (TMDCs) and drawn increasing attention due to potential applications of these materials in light‐emitting diodes, valleytronic devices as well as for being a testbed for understanding many‐body phenomena. Therefore, it is important to enhance the trion emission and its stability. In this study, a MoSe 2 /FePS 3 van der Waals heterostructure (vdWH) with type‐I band alignment is constructed, which allows for carriers injection from FePS 3 to MoSe 2 . At low temperatures, the neutral exciton (X 0 ) emission in this vdWH is almost completely suppressed. The I Trion / I x0 intensity ratio increases from 0.44 in a single MoSe 2 monolayer to 20 in this heterostructure with the trion charging state changing from negative in the monolayer to positive in the heterostructure. The optical pumping with circularly polarized light shows a 14% polarization for the trion emission in MoSe 2 /FePS 3 . Moreover, forming such type‐I vdWH also gives rise to a 20‐fold enhancement of the room temperature photoluminescence from monolayer MoSe 2 . These results demonstrate a novel approach to convert excitons to trions in monolayer 2D TMDCs via interlayer doping effect using type‐I band alignment in vdWH.