Engineering Radiative Energy Transfer and Directional Excitonic Emission in van der Waals Heterostructures

Abstract

AbstractControlling excitonic energy transfer in 2D van der Waals (vdW) heterostructures is crucial for photonic and optoelectronic applications. Recent studies suggest that the interlayer energy transfer in vdW heterostructures is strongly correlated with the vertical interlayer spacing. However, the interlayer coupling with large separations (>20 nm) when the radiative energy transfer is dominant has not been studied yet. In this case, excitons as radiative dipole sources are able to control the light field. Here, the thickness dependency of radiative energy transfer in vertical vdW heterostructures of WS2 (tungsten disulfide)/hBN (hexagonal boron nitride)/WS2 is studied. The excitonic emission of WS2/hBN and WS2/hBN/WS2 heterostructures is engineered with the intensity ratios of heterostructures to monolayers ranging from 5% to 250%. More importantly, by changing the stacking order to control whether forward or backward emission is collected, a controllable directivity of the excitonic emission from 0.6 to 6.0 is achieved. In theory, the tunability to high‐index/mid‐index interferences and dipole–dipole far‐field coupling is attributed. The outcomes of the study on the radiative energy transfer of vdW heterostructures containing 1Ls (monolayers) with excitonic effects and MLs (multilayers) with high refractive indices will pave the way toward the realization of all vdW nanophotonics.