Utilizing Electroplex Emission to Achieve External Quantum Efficiency up to 18.1% in Nondoped Blue OLED

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Organic light-emitting diodes (OLEDs) are crucial for displays and lighting.
• Enhancing OLED performance, particularly external quantum efficiency (EQE), remains a key research challenge.
• Thermally activated delayed fluorescence (TADF) is a common strategy for high efficiency.

Purpose of the Study:

• To explore electroplex emission as a novel mechanism for enhancing OLED performance.
• To synthesize and investigate new donor-acceptor molecules for blue-emitting OLEDs.
• To demonstrate the potential of electroplex emission beyond TADF.

Main Methods:

• Synthesis of three novel donor-acceptor molecules (3Cz-Ph-CN, 3Cz-mPh-CN, 3Ph-Cz-CN) with twisted structures.
• Fabrication and characterization of nondoped blue OLED devices utilizing these molecules.
• Investigation of emission properties at the interface between the emitting and electron-transporting layers.

Main Results:

• Achieved high external quantum efficiency (EQE) of 18.1% in blue OLEDs through electroplex emission.
• Demonstrated control over emission wavelength within the blue region.
• Observed an unprecedented EQE of 27.4% when 3Ph-Cz-CN was used as a host in orange phosphorescent OLEDs.

Conclusions:

• Electroplex emission is a viable and effective strategy for enhancing OLED performance.
• The synthesized donor-acceptor molecules show promise for efficient blue and host materials.
• This work presents an alternative to TADF for achieving high-efficiency OLEDs.