heterostructures*

Ultrafast charge transfer processes provide a facile way to create interlayer excitons in directly contacted transition metal dichalcogenide (TMD) layers. More sophisticated heterostructures composed of TMD/hBN/TMD enable new ways to control interlayer exciton properties and achieve novel exciton phenomena, such as exciton insulators and condensates, where longer lifetimes are desired. In this work, we experimentally study the charge transfer dynamics in a heterostructure composed of a 1-nm-thick hBN spacer between MoSe₂ and WSe₂ monolayers. We observe the hole transfer from MoSe₂ to WSe₂ through the hBN barrier with a time constant of 500 ps, which is over three orders of magnitude slower than that between TMD layers without a spacer. Furthermore, we observe strong competition between the charge transfer process and intralayer exciton-exciton annihilation processes at high excitation densities. Our work opens possibilities to understand charge transfer pathways in TMD/hBN/TMD heterostructures for the efficient generation and control of interlayer excitons.