Highly Efficient Deep-Red Non-Doped Diodes Based on a T-Shape Thermally Activated Delayed Fluorescence Emitter

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Device simplification is crucial for organic light-emitting diodes (OLEDs).
• Achieving efficient deep-red emission remains a significant challenge in OLED technology.

Purpose of the Study:

• To report a novel deep-red thermally activated delayed fluorescence (TADF) molecule, pTPA-DPPZ.
• To investigate its molecular structure, photophysical properties, and performance in OLED devices.

Main Methods:

• Synthesis and characterization of the pTPA-DPPZ molecule.
• Fabrication of a bilayer OLED device using pTPA-DPPZ as the emissive layer.
• Measurement of photoluminescence quantum yield (PLQY), electroluminescence (EL) characteristics, and external quantum efficiency (EQE).

Main Results:

• The pTPA-DPPZ molecule exhibits a T-shaped structure with triphenylamine (TPA) donors and a dipyridophenazine (DPPZ) acceptor.
• Achieved a ~90-fold increase in radiation rate constant (10^7 s⁻¹), near-unity reverse intersystem crossing (RISC) efficiency, and 87% PLQY.
• The OLED device demonstrated record EQEs of 12.3% (max) and 10.4% at 1000 nits, with deep-red emission and high color purity.

Conclusions:

• The pTPA-DPPZ molecule enables efficient deep-red emission through optimized molecular design and packing.
• The developed molecule significantly advances the performance of deep-red OLEDs.
• This work offers a promising pathway for simplified and high-performance deep-red OLEDs.