Atomically thin semiconductors made from transition metal dichalcogenides (TMDs) are model systems for investigations of strong light-matter interactions and applications in nanophotonics, optoelectronics and valleytronics. However, the photoluminescence spectra of TMD monolayers display a large number of features that are particularly challenging to decipher. On a practical level, monochromatic TMD-based emitters would be beneficial for low-dimensional devices, but this challenge is yet to be resolved. Here, we show that graphene, directly stacked onto TMD monolayers, enables single and narrow-line photoluminescence arising solely from TMD neutral excitons. This filtering effect stems from complete neutralization of the TMD by graphene, combined with selective non-radiative transfer of long-lived excitonic species to graphene. Our approach is applied to four tungsten- and molybdenum-based TMDs and establishes TMD/graphene heterostructures as a unique set of optoelectronic building blocks that are suitable for electroluminescent systems emitting visible and near-infrared photons at near THz rate with linewidths approaching the homogeneous limit.

中文翻译：

---

用石墨烯过滤原子薄半导体的光致发光光谱。

由过渡金属二氢硫化物（TMD）制成的原子薄半导体是用于研究强光物质相互作用及其在纳米光子学，光电子学和Valleytronics中的应用的模型系统。但是，TMD单层的光致发光光谱显示出许多特征，这些特征对于解密尤其具有挑战性。从实用的角度来看，基于单色TMD的发射器对于低尺寸器件将是有益的，但这一挑战尚待解决。在这里，我们显示了直接堆叠在TMD单层上的石墨烯可以实现仅由TMD中性激子产生的单线和窄线光致发光。这种过滤效果源于石墨烯对TMD的完全中和，以及长寿命激子物种向石墨烯的选择性非辐射转移。