Yue Yuan-Yuan, Zhao Le-Yi, Han Dan-Ao, Wang Lei, Wang Hai-Yu, Gao Bing-Rong, Sun Hong-Bo
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China.
School of Management Science and Information Engineering, Jilin University of Finance and Economics, Changchun 130117, China.
Phys Chem Chem Phys. 2021 Oct 13;23(39):22430-22436. doi: 10.1039/d1cp02455h.
Since excitonic quasiparticles, including excitons, trions and charges, have a great influence on the photoelectric characteristics of two-dimensional (2D) transition metal dichalcogenides (TMDs), systematic explorations of the trion dynamics and charge photogeneration in 2D TMDs are important for their future optoelectronic applications. Here, broadband femtosecond transient absorption spectroscopic experiments are performed first to investigate the peak shifting and broadening kinetics in MoS nanosheets in solution prepared by liquid phase exfoliation (LPE-MoS, ∼9 layers, 9L), which reveal that the binding energies for the A-, B-, and C-exciton states are ∼77 meV, ∼76 meV, and -70 meV (the energy difference between free charges and excitons; the negative sign for C-excitons means a spontaneous dissociation nature in band-nesting regions), respectively. Then, the trion dynamics and charge photogeneration in LPE-MoS nanosheets have been studied in detail, demonstrating that they are comparable to those in chemical vapor deposition grown MoS films (1L-, 3L- and 7L-MoS). These experimental results suggest that LPE-TMD nanosheets also have the potential for use in charge-related optoelectronic devices based on 2D TMDs.
由于包括激子、三重子和电荷在内的激子准粒子对二维（2D）过渡金属二硫属化物（TMD）的光电特性有很大影响，系统探索二维TMD中的三重子动力学和电荷光生过程对于其未来的光电器件应用至关重要。在此，首先进行了宽带飞秒瞬态吸收光谱实验，以研究通过液相剥离法制备的溶液中MoS纳米片（LPE-MoS，约9层，9L）的峰位移动和展宽动力学，结果表明A-、B-和C-激子态的结合能分别约为77 meV、76 meV和-70 meV（自由电荷与激子之间的能量差；C-激子的负号表示在能带嵌套区域的自发解离性质）。然后，详细研究了LPE-MoS纳米片中的三重子动力学和电荷光生过程，结果表明它们与化学气相沉积生长的MoS薄膜（1L-、3L-和7L-MoS）中的情况相当。这些实验结果表明，LPE-TMD纳米片在基于二维TMD的电荷相关光电器件中也具有应用潜力。
