Li Yang, Stolte Nore, Li Baikui, Li Hui, Cheng Guanghui, Pan Ding, Wang Jiannong
Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Nanoscale. 2019 Jul 28;11(28):13552-13557. doi: 10.1039/c9nr02862e. Epub 2019 Jul 10.
Monolayer transition metal dichalcogenides (TMDCs) are an ideal platform for multi-carrier bound states, the excitons and trions of which have been well identified and investigated. However, the formation and identification of biexcitons with certain configurations are more complicated. Here, we report a strategy to generate the hole-trion bound state, i.e. excited-state biexcitons, in a graphene/WS van der Waals heterostructure, the formation of which is attributed to the charge transfer and exciton dissociation at the hetero-interface. The biexciton nature is confirmed by excitation-power dependent, helicity-resolved, and time-resolved photoluminescence measurements. This hole-trion bound state features a thermal activation energy of ∼32 meV, rendering a stable excited-state biexciton emission up to 330 K. Moreover, the emission behavior of the excited-state biexcitons can be tuned by modifying the charge transfer process at the hetero-interface via electrostatic gating. Our results will benefit to further understanding the complex multi-carrier interactions in 2D semiconductors and related heterostructures.
单层过渡金属二硫属化物（TMDCs）是研究多载流子束缚态的理想平台，其激子和三激子已得到充分识别和研究。然而，具有特定构型的双激子的形成和识别更为复杂。在此，我们报道了一种在石墨烯/WS范德华异质结构中产生空穴 - 三激子束缚态（即激发态双激子）的策略，其形成归因于异质界面处的电荷转移和激子解离。通过依赖于激发功率、螺旋度分辨和时间分辨的光致发光测量证实了双激子的性质。这种空穴 - 三激子束缚态的热激活能约为32毫电子伏特，使得在高达330 K的温度下仍能实现稳定的激发态双激子发射。此外，通过静电门控改变异质界面处的电荷转移过程，可以调节激发态双激子的发射行为。我们的结果将有助于进一步理解二维半导体及相关异质结构中复杂的多载流子相互作用。
