Free Trions with Near-Unity Quantum Yield in Monolayer MoSe₂

Abstract

Trions, quasiparticles composed of an electron–hole pair bound to a second electron and/or hole, are many-body states with potential applications in optoelectronics. Trions in monolayer transition metal dichalcogenide (TMD) semiconductors have attracted recent interest due to their valley/spin polarization, strong binding energy, and tunability through external gate control. However, low materials quality (i.e., high defect density) has hindered efforts to understand the intrinsic properties of trions. The low photoluminescence (PL) quantum yield (QY) and short lifetime of trions have prevented harnessing them in device applications. Here, we study the behavior of trions in a series of MoSe2 monolayers, with atomic defect density varying by over 2 orders of magnitude. The QY increases with decreasing defect density and approaches unity in the cleanest material. Simultaneous measurement of the PL lifetime yields both the intrinsic radiative lifetime and the defect-dependent nonradiative lifetime. The long lifetime of ∼230 ps of trions allows direct observation of their diffusion.

Macroscopic transition metal dichalcogenides monolayers with uniformly high optical quality

“…From the difference of the exciton and trion energies, we obtain the trion binding energy of 28.3 0.6 meV (Supplementary Fig. 7a ), consistent with previously reported values 30 . The PL intensities of the exciton and trion both vary by 14%, and their ratio is 0.84 0.10 (Supplementary Fig.…”

“…1c shows sharp contrast between the bare and encapsulated MoSe 2 MML. The bare MML PL is dominated by broad in-gap state (IGS) emission, spreading from ~1.60 eV to ~1.63 eV 30 . The encapsulated MML, however, features two sharp peaks at 1.653 and 1.625 eV, with full width at half maximum (FWHM) of 7.1 0.4 and 8.2 0.6 meV, respectively, corresponding to MoSe 2 monolayer A exciton and trion emission 30 , while IGS emission below the excitonic resonances is strongly suppressed.…”

Recent progress in 2D hybrid heterostructures from transition metal dichalcogenides and organic layers: properties and applications in energy and optoelectronics fields

“…6h), the emission intensity increased correspondingly due to the increased quantum yield of exciton emission compared to that of trion transition. 128 In addition, the report included a small yet distinct change (∼3 cm −1 ) in the in-plane Raman shift (E 1 2g ) from the p-doped sample compared to the control, which was attributed to the softened electron–phonon interaction. 129…”

“…6h), the emission intensity increased correspondingly due to the increased quantum yield of exciton emission compared to that of trion transition. 128 In addition, the report included a small yet distinct change (∼3 cm −1 ) in the in-plane Raman shift (E 1 2g ) from the p-doped sample compared to the control, which was attributed to the softened electron-phonon interaction. 129 Organic molecules bearing electric dipoles may develop localized electric fields on ultrathin TMDs, modulating charge densities like applying gate voltage on semiconducting channels.…”

Customizing Radiative Decay Dynamics of Two-Dimensional Excitons via Position- and Polarization-Dependent Vacuum-Field Interference

“…It has been known that undesired creations of material factors such as detects, strain, deformations, and electrostatic doping can affect the decay channels of excitons locally and increase spatial inhomogeneity in the PL intensity and line shape. 25,29,46 interaction between the vacuum-field fluctuations and excitons (Supporting Information Section S7).…”