Enhanced interlayer neutral excitons and trions in MoSe₂/MoS₂/MoSe₂ trilayer heterostructure

Van der Waals heterostructures have recently emerged, in which two distinct transitional metal dichalcogenide (TMD) monolayers are stacked vertically to generate interlayer excitons (IXs), offing new opportunites for the design of optoelectronic devices. However, the bilayer heterostructure with type-II band alignment can only produce low quantum yield. Here, we present the observation of interlayer neutral excitons and trions in the MoSe₂/MoS₂/MoSe₂ trilayer heterostructure (Tri-HS). In comparison to the 8 K bilayer heterostructure, the addition of a MoSe₂ layer to the Tri-HS can significantly increase the quantum yield of IXs. It is believed the two symmetrical type-II band alignments formed in the Tri-HS could effectively promote the IX radiation recombination. By analyzing the photoluminescence (PL) spectrum of the IXs at cryogenic temperature and the power dependence, the existence of the interlayer trions was confirmed. Our results provide a promising platform for the development of more efficient optoelectronic devices and the investigation of new physical properties of TMDs.