Engineering WS2 exciton polarization by an anisotropic organic substrate

Controlling the polarization of the emitted light at room temperature is critical for the transition metal dichalcogenides monolayer based photonic devices. One way is to integrate the complicated man-made photonic structures with the monolayer where the photoluminescence (PL) couples with linearly polarized radiation. However, the PL polarization of the monolayer is fixed and cannot be tuned in these structures. In this work, through transferring the WS2 monolayer onto a simple organic β-perylene (Pe) layer, we show the PL of the WS2 monolayer can be linearly polarized by virtue of the coupling with the anisotropic modes, which are created due to the reflection of photons between the surface of the Pe substrate. More importantly, we demonstrate tunable linearly polarized excitonic emission from the WS2 monolayer by varying the thickness of the β-Pe substrate. Our work paves the way to engineer the exciton polarization of 2D materials without complicated fabrication structures at room temperature.