Efficient Energy Transfer in In2Se3-MoSe2 van der Waals Heterostructures

We show that bilayer a-phase In2Se3 and monolayer MoSe2 forma 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 IMoSe2 to In2Se3. This is further confirmed by the observation that the photocarrier lifetime in the heterostructure is similar to monolayer MoSe, 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 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 a-In2Se3 ultrathin layers can be effectively integrated as light-absorbing layers with other transition metal dichalcogenides for novel optoelectronic applications.