Blue organic light-emitting diodes realizing external quantum efficiency over 25% using thermally activated delayed...

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Efficient blue organic light-emitting diodes (OLEDs) are crucial for advanced displays and lighting.
• Thermally activated delayed fluorescence (TADF) offers a pathway to high electroluminescence efficiency.
• Developing effective blue TADF emitters faces challenges in molecular design.

Purpose of the Study:

• To design and synthesize novel TADF emitters for efficient blue OLEDs.
• To address the challenges of small singlet-triplet energy gap (ΔE_ST), large oscillator strength (f), and high S₁ energy.
• To investigate the photophysical properties and electroluminescence performance of new TADF materials.

Main Methods:

• Molecular design incorporating specific structural features for TADF properties.
• Photoluminescence spectroscopy to assess emission characteristics and up-conversion yield.
• Fabrication and characterization of OLED devices using the synthesized emitters.

Main Results:

• Development of CCX-I and CCX-II TADF emitters exhibiting blue photoluminescence.
• Achieved high triplet-to-singlet up-conversion yield and horizontally oriented transition dipole moments.
• Demonstrated a blue OLED with CCX-II achieving a high external quantum efficiency (EQE) of 25.9%.

Conclusions:

• CCX-I and CCX-II successfully meet the stringent requirements for efficient blue TADF emitters.
• The horizontally oriented transition dipole moments contribute to enhanced electroluminescence efficiency.
• The achieved EQE represents a significant advancement in blue OLED performance.