Pure-Green Circularly Polarized Multiple Resonance Thermally Activated Delayed Fluorescence Enantiomers with...

Area of Science:

• Organic Electronics
• Materials Science
• Photochemistry

Background:

• Helicene-based materials for circularly polarized luminescence (CPL) in organic light-emitting diodes (OLEDs) exhibit poor color purity.
• Existing CP-OLEDs struggle to balance efficient CPL with high color fidelity.

Purpose of the Study:

• To introduce a novel molecular engineering strategy to overcome the color purity limitations of helicene-based CPL materials.
• To develop high-performance emitters for pure green circularly polarized organic light-emitting diodes (CP-OLEDs) with efficient thermally activated delayed fluorescence (TADF).

Main Methods:

• Replaced continuous fused benzene rings in helicenes with a multiple resonance (MR) framework featuring discontinuous fused rings.
• Synthesized and characterized novel green BN[7]helicene-based emitters, (P/M)-DBN-mICz.
• Fabricated and evaluated CP-OLED devices using the developed emitters.

Main Results:

• The new MR framework effectively suppresses vibrations and enhances charge transfer, leading to high color purity and CPL activity.
• The (P/M)-DBN-mICz emitters demonstrated bright, narrowband green emission (512 nm, FWHM 25 nm) with high CPL.
• CP-OLEDs achieved pure green emission (516 nm, FWHM 27 nm), the purest reported to date, with high external quantum efficiencies (up to 37.3%) and electroluminescence dissymmetry factors.

Conclusions:

• The novel MR framework is a viable strategy for designing high-purity CPL emitters.
• The developed BN[7]helicene derivatives represent a significant advancement in CP-OLED technology, offering efficient and pure green emission.
• This work paves the way for next-generation displays and lighting applications requiring high-performance circularly polarized light.