Hot-Carrier Extraction Prevailing over Multiple-Exciton Generation in Two-Dimensional Semiconductor Heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• The Shockley-Queisser limit restricts solar cell efficiency.
• Multiple-exciton generation (MEG) offers a route to surpass this limit.
• Monolayer transition metal dichalcogenides are promising candidates for MEG studies.

Purpose of the Study:

• Investigate MEG in monolayer Molybdenum Ditelluride (MoTe2).
• Determine the energy threshold and efficiency of MEG in MoTe2.
• Explore the origins of efficient MEG and its competition with hot-carrier extraction.

Main Methods:

• Experimental investigation of MEG in monolayer MoTe2.
• Fabrication and characterization of MoTe2/Tungsten Diselenide (WSe2) type I heterostructures.
• Analysis of energy thresholds and conversion efficiencies.

Main Results:

• Monolayer MoTe2 exhibits MEG with an energy threshold of 2.22 eV.
• A high MEG conversion efficiency of 90% was achieved.
• Impact ionization is identified as the likely mechanism for exciton multiplication.

Conclusions:

• Monolayer MoTe2 demonstrates significant potential for efficient light harvesting.
• The findings suggest applications in advanced hot-carrier devices.
• MEG in MoTe2 provides a viable strategy to enhance photon-to-electron conversion efficiency.