Thermal assisted up-conversion electroluminescence in quantum dot light emitting diodes

Area of Science:

• Optoelectronics
• Materials Science
• Quantum Dot Technology

Background:

• Up-conversion electroluminescence (UCEL) involves emitting photons with higher energy than excitation electrons, observed in quantum-dot light-emitting diodes (QLEDs).
• Understanding the charge injection dynamics is crucial for optimizing UCEL device performance.

Purpose of the Study:

• To investigate the mechanism behind up-conversion electroluminescence in quantum-dot devices.
• To elucidate the role of thermal energy in the charge injection dynamics.
• To explore sub-bandgap turn-on mechanisms in QLEDs.

Main Methods:

• Experimental investigation of temperature-dependent electroluminescence in quantum-dot devices.
• Theoretical analysis of charge injection dynamics.
• Validation through further theoretical deduction and experimental results.

Main Results:

• Hole injection into quantum dots via thermal-assisted thermionic emission was observed at sub-bandgap voltages.
• This thermal-assisted hole injection enables sub-bandgap turn-on and up-conversion electroluminescence.
• The study confirms thermal-assisted hole injection as a universal mechanism for UCEL.

Conclusions:

• The charge injection process and sub-bandgap turn-on mechanism for UCEL in QLEDs have been uncovered.
• This research provides a pathway for developing up-conversion devices with power conversion efficiencies exceeding 100%.