Electrically Tunable Valley-Light Emitting Diode (vLED) Based on CVD-Grown Monolayer WS2

Area of Science:

• Condensed Matter Physics
• Materials Science
• Optoelectronics

Background:

• Monolayer transition-metal dichalcogenides (TMDs) possess direct band gaps and strong spin-orbit coupling, enabling unique valley phenomena.
• These properties are crucial for developing valleytronics and light-emitting diodes (LEDs), but require scalable, high-quality materials.
• Current methods using mechanically exfoliated flakes limit practical applications.

Purpose of the Study:

• To demonstrate electrically tunable chiral electroluminescence (EL) from large-area, chemical vapor deposition (CVD)-grown monolayer tungsten disulfide (WS2).
• To investigate the potential of CVD-grown WS2 for fabricating practical 2D optoelectronic devices, specifically valley LEDs.

Main Methods:

• Fabrication of a p-i-n heterojunction using CVD-grown monolayer WS2.
• Characterization of electroluminescence (EL) properties, focusing on chirality contrast and its tunability.
• Electrical modulation of EL properties via forward current.

Main Results:

• Achieved electrically tunable chiral EL from CVD-grown monolayer WS2.
• Demonstrated a high chirality contrast of up to 81% in the overall EL.
• Successfully modulated the chirality contrast by adjusting the forward current.

Conclusions:

• The study presents the first successful demonstration of electrically tunable chiral EL from CVD-grown monolayer WS2.
• The high chirality contrast and tunability highlight the potential of these materials for valleytronics.
• This work enables the development of scalable, unconventional 2D optoelectronic devices, including valley LEDs.