Simultaneous Hosting of Positive and Negative Trions and the Enhanced Direct Band Emission in MoSe2/MoS2Heterostacked Multilayers

Heterostacking of layered transition-metal dichalcogenide (LTMD) monolayers (1Ls) offers a convenient way of designing two-dimensional exciton systems. Here we demonstrate the simultaneous hosting of positive trions and negative trions in heterobilayers made by vertically stacking 1L MoSe2and 1L MoS2. The charge transfer occurring between the 1Ls of MoSe2and MoS2converted the polarity of trions in 1L MoSe2from negative to positive, resulting in the presence of positive trions in the 1L MoSe2and negative trions in the 1L MoS2of the same heterostacked bilayer. Significantly enhanced MoSe2photoluminescence (PL) in the heterostacked bilayers compared to the PL of 1L MoSe2alone suggests that, unlike other previously reported heterostacked bilayers, direct band transition of 1L MoSe2in heterobilayer was enhanced after the vertical heterostacking. Moreover, by inserting hexagonal BN monolayers between 1L MoSe2and 1L MoS2, we were able to adjust the charge transfer to maximize the MoSe2PL of the heteromultilayers and have achieved a 9-fold increase of the PL emission. The enhanced optical properties of our heterostacked LTMDs suggest the exciting possibility of designing LTMD structures that exploit the superior optical properties of 1L LTMDs.