Spontaneous Polarization Induced Photovoltaic Effect In Rhombohedrally Stacked MoS${}_2$

Abstract

Stacking order in van der Waals materials determines the coupling between atomic layers and is therefore key to the materials' properties. By exploring different stacking orders, many novel physical phenomena have been realized in artificial vdW stacks. Recently, 2D ferroelectricity has been observed in zero-degree aligned hBN and graphene-hBN heterostructures, holding promise in a range of electronic applications. In those artificial stacks, however, the single domain size is limited by the stacking-angle misalignment to about 0.1 to 1 $\mu$m, which is incompatible with most optical or optoelectronic applications. Here we show MoS${}_2$ in the rhombohedral phase can host a homogeneous spontaneous polarization throughout few-$\mu$m-sized exfoliated flakes, as it is a natural crystal requiring no stacking and is, therefore free of misalignment. Utilizing this homogeneous polarization and its induced depolarization field (DEP), we build a graphene-MoS${}_2$ based photovoltaic device with high efficiency. The few-layer MoS${}_2$ is thinner than most oxide-based ferroelectric films, which allows us to maximize the DEP and study its impact at the atomically thin limit, while the highly uniform polarization achievable in the commensurate crystal enables a tangible path for up-scaling. The external quantum efficiency of our device is up to 16% at room temperature, over one order larger than the highest efficiency observed in bulk photovoltaic devices, owing to the reduced screening in graphene, the exciton-enhanced light-matter interaction, and the ultrafast interlayer relaxation in MoS${}_2$. In view of the wide range of bandgap energy in other TMDs, our findings make rhombohedral TMDs a promising and versatile candidate for applications such as energy-efficient photo-detection with high speed and programmable polarity.

arXiv comment20 pages, 6 figures

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Cited by in corpus (13)

• General Theory for Bilayer Stacking Ferroelectricity
• Visualizing moiré ferroelectricity via plasmons and nano-photocurrent in graphene/twisted-WSe2 structures
• Stacking-dependent exciton multiplicity in WSe${}_2$ bilayers
• Polarization Saturation in Multi-layered Interfacial Ferroelectrics
• Quantum-Geometric Origin of Out-of-plane Stacking Ferroelectricity
• Unveiling intrinsic bulk photovoltaic effect in atomically thin ReS2
• On the photovoltaic effect asymmetry in ferroelectrics
• Superlubric sliding ferroelectricity
• Plasmonic polarization sensing of electrostatic superlattice potentials
• Two-dimensional electrons at mirror and twistronic twin boundaries in van der Waals ferroelectrics
• Photoluminescence Detection of Polytype Polarization in r-MoS2 Enabled by Asymmetric Dielectric Environments
• Shift current response in twisted double bilayer graphenes
• Shear-Mode Raman Imaging of Ferroelectric Switching in Multilayer 3$R$-MoS${}_2$