Efficient Energy Transfer in In₂Se₃-MoSe₂ van der Waals Heterostructures

We show that bilayer α-phase In₂Se₃ and monolayer MoSe₂ form a type-I band alignment, with both the conduction band minimum and the valence band maximum located in MoSe₂. Samples were fabricated by a two-step chemical vapor deposition method. The photoluminescence yield of the heterostructure sample was found to be similar to monolayer MoSe₂, indicating the lack of an efficient charge transfer from MoSe₂ to In₂Se₃. This is further confirmed by the observation that the photocarrier lifetime in the heterostructure is similar to monolayer MoSe₂, showing the lack of layer separation of the electrons and holes. Efficient energy transfer from In₂Se₃ to MoSe₂ was observed by the sevenfold enhancement of the differential reflection signal in the heterostructure and its ultrashort rising time. Furthermore, we observed significant photoluminescence quenching in heterostructures formed by bulk In₂Se₃ and monolayer MoSe₂, which suggests efficient charge transfer and therefore type-II band alignment. These findings suggest that α-In₂Se₃ ultrathin layers can be effectively integrated as light-absorbing layers with other transition metal dichalcogenides for novel optoelectronic applications.