Department of Physics, Sogang University, Seoul 04107, South Korea.
Department of Energy Science, Sungkyunkwan University, Suwon 16419, South Korea.
J Phys Chem Lett. 2023 May 11;14(18):4259-4265. doi: 10.1021/acs.jpclett.3c00305. Epub 2023 May 1.
Monolayer transition metal dichalcogenides (TMDs) have been extensively studied for their optoelectronic properties and applications. However, even at moderate exciton densities, their light-emitting capability is severely limited by Auger-type exciton-exciton annihilation (EEA). Previous work on EEA used oversimplified models in the presence of excitonic complexes, resulting in seriously underestimated values for the Auger coefficient. In this work, we transferred monolayer WS on a gold substrate with hBN encapsulation, where excitons persist as the main species at 3-300 K via metal proximity. We numerically solved the rate equation for excitons to accurately determine the Auger coefficient as a function of temperature by considering laser pulse width and spatially inhomogeneous exciton distribution. We found that the Auger coefficient consists of temperature-dependent and independent terms, consistent with a theoretical model for direct and exchange processes, respectively. We believe that our results provide a guide for enhancing the luminescence quantum yield of TMDs.
单层过渡金属二卤族化合物（TMDs）因其光电特性及其应用而得到了广泛的研究。然而，即使在中等激子密度下，它们的发光能力也受到激子-激子湮灭（EEA）的限制。以前关于 EEA 的工作在存在激子复合物的情况下使用了过于简化的模型，导致 Auger 系数被严重低估。在这项工作中，我们将单层 WS 转移到具有 hBN 封装的金衬底上，其中激子通过金属接近作为主要物种在 3-300 K 下存在。我们通过考虑激光脉冲宽度和空间非均匀激子分布，数值求解激子的速率方程，以准确确定温度作为函数的 Auger 系数。我们发现 Auger 系数由温度相关和独立的项组成，分别与直接和交换过程的理论模型一致。我们相信我们的结果为提高 TMDs 的发光量子产率提供了指导。
