Van der Waals Photodetector with an Integrated WS2 Light-Harvesting Antenna.

The responsivity of graphene-based photodetectors can be improved by forming heterostructures with other 2D materials and by further coupling to nanoparticles or quantum dots. In this study, we demonstrate that the photoresponse of a Graphene/MoSe2/Graphene photodetector can be further enhanced by an external WS2 bilayer acting as a light-harvesting antenna. The WS2 bilayer is positioned outside the electronic pathway; thus, it does not directly contribute any photoexcited carriers. However, we observe a responsivity enhancement of up to 18 times, which can be explained by energy transfer from WS2 to graphene and the MoSe2 layer. Harnessing the excitonic properties of transition metal dichalcogenides (TMDs) as optical antennas defines a new strategy for photodetection.