Tunable Localized Charge Transfer Excitons in Nanoplatelet-2D Chalcogenide van der Waals Heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Interlayer charge transfer (CT) excitons in 2D-2D van der Waals heterostructures (vdWHs) are well-studied but difficult to localize.
• Spatial localization of CT excitons in vdWHs typically requires precise layer twisting, limiting practical applications.

Purpose of the Study:

• To demonstrate the formation and localization of CT excitons in mixed-dimensional nanoplate-2D material heterostructures (N2DHs).
• To investigate the tunability of CT exciton resonance energy in N2DHs.
• To explore the potential of N2DHs for next-generation photonic devices.

Main Methods:

• Fabrication of N2DHs using MoSe2 and WSe2 monolayers with CdSe/CdS core/shell nanoplates (NPLs).
• Utilized tip-enhanced photoluminescence (TEPL) at room temperature to resolve spectral signatures of CT excitons at the 2D/single-NPL heterointerface.
• Systematically varied 2D materials, NPL shell thickness, and applied electric fields to tune exciton energy.

Main Results:

• Successfully formed and localized CT excitons at the heterointerface within N2DHs.
• Achieved up to 100 meV tuning of exciton resonance energy by manipulating material composition and external electric fields.
• Demonstrated room-temperature spectral signatures of CT excitons, confirming their presence and localization.

Conclusions:

• N2DHs offer a viable strategy to overcome the localization challenges of CT excitons in traditional vdWHs.
• The demonstrated tunability of exciton resonance energy in N2DHs is crucial for designing advanced optoelectronic devices.
• This work represents a significant advancement towards realizing highly tunable N2DH-based photonic applications.