Layer-Dependent Electron Transfer and Recombination Processes in MoS₂/WSe₂ Multilayer Heterostructures

Understanding and controlling the charge transfer processes of two-dimensional (2D) materials are fundamental for the optimized device performance based on 2D semiconductors and heterostructures. The charge transfer rate is very robust in transition metal disulfide (TMD) heterostructures with type II band alignments, which can be manipulated by intercalating a dielectric layer like hBN to isolate the donor and acceptor monolayers. This study shows that there is an alternative way to change the electron transfer and recombination rates in the case of nLMoS₂/mLWSe₂ multilayer heterostructures, where the donor-acceptor distance is maintained, but the rate of electron transfer is strongly layer dependent and shows asymmetry for the layer number of donor and acceptor monolayers. Especially, the 1LMoS₂/2LWSe₂ heterostructure slows electron transfer and charge recombination rates ∼2.3 and ∼12 times that of the 1LMoS₂/1LWSe₂ heterostructure, respectively, which have been competitive with that in the 1LMoS₂/hBN/1LWSe₂ heterostructure. From an application perspective, the noninterfacial electron transfer in which photogenerated electrons should across more than one atomically thin layer is not favorable due to the built-in electric field established by the initial interfacial electron transfer.