New Pathway for Hot Electron Relaxation in Two-Dimensional Heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) heterostructures from transition-metal dichalcogenides are promising for optoelectronics.
• Key properties like ultrafast charge dynamics and interlayer energy transfer are not fully understood.
• Understanding these dynamics is vital for advancing photovoltaic and optoelectronic device applications.

Purpose of the Study:

• To investigate photoexcited electron/hole dynamics in 2D heterostructures.
• To explore the MoS2/WSe2 interface, known for its type II band alignment.
• To elucidate ultrafast charge and energy transfer mechanisms at the atomic layer interface.

Main Methods:

• Employed time-dependent density functional theory (TD-DFT) in the time domain.
• Simulated photoexcited electron and hole dynamics.
• Analyzed charge carrier lifetimes and relaxation pathways.

Main Results:

• Observed ultrafast charge dynamics with carrier lifetimes ranging from tens to hundreds of femtoseconds.
• Discovered a novel interfacial pathway for hot electron relaxation through interlayer hopping.
• Demonstrated that this interfacial pathway is significantly faster than intralayer relaxation.

Conclusions:

• The MoS2/WSe2 heterostructure exhibits rapid charge carrier dynamics.
• Interlayer hopping provides an efficient pathway for hot electron relaxation in 2D heterostructures.
• This finding is critical for understanding ultrafast (<1 ps) photoinduced charge and energy transfer processes in these advanced materials.