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Spontaneous-polarization-induced photovoltaic effect in rhombohedrally stacked MoS2
Nature Photonics ( IF 35.0 ) Pub Date : 2022-05-26 , DOI: 10.1038/s41566-022-01008-9
Dongyang Yang , Jingda Wu , Benjamin T. Zhou , Jing Liang , Toshiya Ideue , Teri Siu , Kashif Masud Awan , Kenji Watanabe , Takashi Taniguchi , Yoshihiro Iwasa , Marcel Franz , Ziliang Ye

Stacking order in van der Waals materials determines the coupling between atomic layers and is therefore the key to materials’ properties. Recently, ferroelectricity, a phenomenon exhibiting reversible spontaneous electrical polarization, has been observed in zero-degree aligned van der Waals structures. In these artificial stacks, the single-domain size is limited by angle misalignment. Here we show that naturally rhombohedrally stacked MoS2 can host a homogeneous spontaneous polarization throughout the exfoliated flakes, free of misalignment. Utilizing this homogeneous polarization and its induced depolarization field, we build a graphene–MoS2-based photovoltaic device with high efficiency. Few-layer MoS2 is thinner than most oxide-based ferroelectric films, which allows us to maximize the depolarization field and study its impact at the atomically thin limit, whereas the highly uniform polarization in the commensurate crystal enables a tangible path for upscaling. 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, exciton-enhanced light–matter interaction and ultrafast interlayer relaxation. Our findings make rhombohedral transition metal dichalcogenides a promising candidate for applications such as energy-efficient photodetection with high speed and programmable polarity.



中文翻译:

菱形堆叠 MoS2 中的自发极化诱导光伏效应

范德华材料中的堆叠顺序决定了原子层之间的耦合,因此是材料性能的关键。最近,在零度对齐的范德华结构中观察到铁电性,一种表现出可逆自发极化的现象。在这些人工堆叠中,单畴尺寸受到角度未对准的限制。在这里,我们表明自然菱面体堆叠的 MoS 2可以在整个剥落的薄片中承载均匀的自发极化,没有错位。利用这种均匀极化及其诱导的去极化场,我们构建了一种高效的石墨烯-MoS 2基光伏器件。少层MoS 2比大多数基于氧化物的铁电薄膜更薄,这使我们能够最大化去极化场并研究其在原子薄极限下的影响,而相应晶体中高度均匀的极化为放大提供了切实可行的途径。由于石墨烯的屏蔽减少、激子增强的光-物质相互作用和超快的层间弛豫,我们器件的外量子效率在室温下高达 16%,比在体光伏器件中观察到的最高效率高出一个数量级。我们的研究结果使菱面体过渡金属二硫属化物成为具有高速和可编程极性的节能光电探测等应用的有希望的候选者。

更新日期:2022-05-27
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