High efficiency blue organic light-emitting diodes with below-bandgap electroluminescence

Area of Science:

• Materials Science
• Organic Electronics
• Device Physics

Background:

• High triplet energy interlayers in blue organic light-emitting diodes (OLEDs) create energetic barriers, leading to high operating voltages and reduced efficiency.
• Existing approaches often focus on synthesizing complex organic molecules, which is challenging and costly.

Purpose of the Study:

• To design and implement a novel interlayer strategy for blue OLEDs to overcome efficiency limitations.
• To reduce the turn-on voltage and improve the external quantum efficiency (EQE) of blue OLED devices.
• To explore alternative device engineering solutions beyond complex material synthesis.

Main Methods:

• Designed a low triplet energy, high mobility hole transporting interlayer.
• Incorporated an interface exciplex to confine excitons at the emissive layer/electron transporting material interface.
• Fabricated and characterized blue thermally activated delay fluorescent (TADF) OLED devices.

Main Results:

• Achieved a below-bandgap turn-on voltage of 2.5 V.
• Attained a maximum external quantum efficiency (EQE) of 41.2%.
• Demonstrated suppressed efficiency roll-off, maintaining an EQE of 34.8% at 1000 cd m⁻².

Conclusions:

• The developed interlayer and interface exciplex effectively reduce voltage and enhance efficiency in blue OLEDs.
• This device engineering approach offers a viable alternative to complex organic material synthesis for improved OLED performance.
• The findings pave the way for future advancements in OLED technology through innovative device design.