Photoluminescence quenching and charge transfer in artificial heterostacks of monolayer transition metal dichalcogenides and few-layer black phosphorus.

Transition metal dichalcogenides monolayers and black phosphorus thin crystals are emerging two-dimensional materials that demonstrated extraordinary optoelectronic properties. Exotic properties and physics may arise when atomic layers of different materials are stacked together to form van der Waals solids. Understanding the important interlayer couplings in such heterostructures could provide avenues for control and creation of characteristics in these artificial stacks. Here we systematically investigate the optical and optoelectronic properties of artificial stacks of molybdenum disulfide, tungsten disulfide, and black phosphorus atomic layers. An anomalous photoluminescence quenching was observed in tungsten disulfide-molybdenum disulfide stacks. This was attributed to a direct to indirect band gap transition of tungsten disulfide in such stacks while molybdenum disulfide maintains its monolayer properties by first-principles calculations. On the other hand, due to the strong build-in electric fields in tungsten disulfide-black phosphorus or molybdenum disulfide-black phosphorus stacks, the excitons can be efficiently splitted despite both the component layers having a direct band gap in these stacks. We further examine optoelectronic properties of tungsten disulfide-molybdenum disulfide artificial stacks and demonstrate their great potentials in future optoelectronic applications.