Quantum Coherence Facilitates Efficient Charge Separation at a MoS2/MoSe2 van der Waals Junction

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Two-dimensional transition metal dichalcogenides (MX2) are promising for optoelectronics and photovoltaics.
• Efficient charge separation is crucial for light-to-electricity conversion.
• Coulomb interactions in MX2 typically hinder charge separation at heterojunctions.

Purpose of the Study:

• To investigate the mechanisms behind efficient charge transfer at MX2 heterojunctions.
• To explain the experimental observation of rapid charge separation despite strong Coulombic forces.
• To provide atomistic insights into excitation dynamics in MX2.

Main Methods:

• Time-domain density functional theory (TD-DFT).
• Nonadiabatic (NA) molecular dynamics simulations.
• Analysis of quantum coherence and donor-acceptor delocalization.

Main Results:

• Quantum coherence and donor-acceptor delocalization facilitate rapid charge transfer at MoS2/MoSe2 interfaces.
• Electron delocalization is greater than hole delocalization, leading to faster electron transfer.
• Subpicosecond electron and hole transfer times were observed, consistent with experimental data.
• Out-of-plane Mo-X vibrational modes and lighter S atoms enhance charge transfer rates.

Conclusions:

• The study reveals that quantum effects, not classical expectations, govern charge separation in MX2 heterojunctions.
• Rapid charge transfer and reduced recombination at interfaces promote efficient, long-lived charge separation.
• These findings offer critical insights for designing advanced 2D materials for optoelectronic applications.