High-performance inverted organic light-emitting diodes with extremely low efficiency roll-off using...

Area of Science:

• Materials Science
• Organic Electronics
• Quantum Dot Technology

Background:

• The electron-injecting layer (EIL) is crucial for achieving high efficiency in inverted organic light-emitting diodes (OLEDs).
• Traditional EILs like ZnO face limitations in optimizing electron injection and charge recombination.

Purpose of the Study:

• To introduce a novel cathode-modified EIL based on ZnS quantum dots (QDs) for inverted OLEDs.
• To evaluate the performance enhancement of inverted OLEDs using ZnS QD EILs compared to conventional ZnO EILs.
• To investigate the impact of different pH values on ZnS QD properties and their effect on device performance.

Main Methods:

• Fabrication of inverted OLEDs with a cathode-modified EIL using ZnS quantum dots.
• Synthesis of ZnS QDs at different pH values (pH 10 and pH 12).
• Characterization of device performance, including turn-on voltage, current efficiency, and efficiency roll-off.

Main Results:

• The ZnS QD EIL significantly improved device performance compared to traditional ZnO EIL.
• The best-performing device achieved a low turn-on voltage of 2.9 V and a maximum current efficiency of 61.5 cd A⁻¹.
• Devices with ZnS-A (pH 10) exhibited minimal efficiency roll-off (0.9% at 1000 cd m⁻² and 4.3% at 5000 cd m⁻²).

Conclusions:

• ZnS quantum dots are a promising material for developing advanced electron-injecting layers in inverted OLEDs.
• The proposed ZnS QD EIL strategy effectively enhances electron injection and charge carrier recombination efficiency.
• This approach offers a viable route to achieving high-performance, efficient inverted OLEDs with reduced efficiency roll-off.