Efficient hot-electron extraction in two-dimensional semiconductor heterostructures by ultrafast resonant transfer

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Energy loss via hot-carrier cooling limits thermodynamic efficiency in optoelectronic devices.
• Efficient hot-electron extraction is crucial for advanced devices but challenging in conventional semiconductors.
• Two-dimensional (2D) layered semiconductor heterostructures offer potential for novel physics and optoelectronics.

Purpose of the Study:

• To investigate hot-electron transfer dynamics in 2D semiconductor heterostructures.
• To explore the potential of WS2-MoTe2 heterostructures for efficient hot-electron extraction.
• To understand the influence of excitation energy on hot-electron transfer efficiency.

Main Methods:

• Broadband micro-area ultrafast spectroscopy was employed.
• Characterization of band alignment in WS2-MoTe2 heterostructures.
• Measurement of hot-electron transfer times and efficiencies.

Main Results:

• A type I band alignment was confirmed in the WS2-MoTe2 heterostructure.
• Ultrafast hot-electron transfer (approximately 60 fs) from MoTe2 to WS2 was observed.
• Hot-electron transfer efficiency increased with excitation energy, reaching 90% for 0.3 eV excess energy.

Conclusions:

• WS2-MoTe2 heterostructures facilitate efficient and ultrafast hot-electron transfer.
• These findings open opportunities for designing ultra-thin absorber and hot-carrier devices.
• The study provides insights into interfacial photoinduced processes in 2D heterostructures for optoelectronics.