Room temperature multi-phonon upconversion photoluminescence in monolayer semiconductor WS₂.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Photon upconversion is an anti-Stokes process where absorbed photon energy is re-emitted at higher energy.
• Previous demonstrations involved rare earth atoms, quantum wells, nanobelts, carbon nanotubes, and atomically thin semiconductors.

Purpose of the Study:

• To demonstrate room temperature photon upconversion in monolayer tungsten disulfide (WS2).
• To investigate the underlying mechanisms of upconversion in this material.

Main Methods:

• Experimental observation of upconversion photoluminescence in monolayer WS2.
• Analysis of energy gain and attribution of the process to specific electronic and phononic interactions.

Main Results:

• Demonstrated a room temperature upconversion photoluminescence process in monolayer WS2.
• Achieved significant energy gain up to 150 meV.
• Attributed the process to transitions involving trions, many phonons, and free exciton complexes.

Conclusions:

• Monolayer WS2 exhibits efficient room temperature photon upconversion.
• The findings are promising for applications in energy harvesting, laser refrigeration, and nanoscale optoelectronics.