Changes in the photoluminescence of ultra-weak interlayer coupled MoSe₂/PbI₂ van der Waals heterostructures

Photo-generated dynamics have been extensively studied in two-dimensional (2D) heterostructures, such as MoSe₂/WSe₂ and MoSe₂/MoS₂. Here, we fabricate few-layer PbI₂ and monolayer MoSe₂ van der Waals (vdW) heterostructures. The excited-wavelength dependent measurements of photoluminescence (PL) and transient dynamic absorption spectra show that there is almost no photo-generated charge transfer between PbI₂ and MoSe₂. PL changes of MoSe₂ are rather dominated by the Fermi level (E_F) modulation through the interlayer charge transfer. Density functional theory calculation shows that binding energies in the heterostructures of MoSe₂/WSe₂ or MoSe₂/MoS₂ are 2–3 times higher than that of the MoSe₂/PbI₂ heterostructure, suggesting the weaker interlayer coupling between MoSe₂ and PbI₂. We propose that the weak interlayer vdW coupling cannot drive the photo-generated interlayer charge transfer while the E_F modulation can be achieved through the interlayer charge transfer. The findings will be helpful to fundamental research and applications for novel optoelectronic devices based on 2D material vdW heterostructures. © 2023 Author(s). Published under an exclusive license by AIP Publishing.