Nanosecond-time-scale delayed fluorescence molecule for deep-blue OLEDs with small efficiency rolloff.

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Organic light-emitting diodes (OLEDs) utilize emitters to generate light.
• Thermally activated delayed fluorescence (TADF) emitters can harvest both singlet and triplet excitons for light emission.
• Deep-blue TADF emitters often suffer from efficiency roll-off at high luminance due to long exciton lifetimes.

Purpose of the Study:

• To design and synthesize a novel deep-blue TADF emitter with a fast exciton lifetime.
• To investigate the relationship between molecular design, activation energy, and spin-orbit coupling in TADF emitters.
• To demonstrate the performance of the new emitter in an OLED device.

Main Methods:

• Molecular design of a donor-acceptor type TADF emitter without heavy metals.
• Simultaneous control of activation energy and spin-orbit coupling.
• Fabrication and characterization of an OLED device utilizing the developed TADF emitter.

Main Results:

• Achieved an extremely fast exciton lifetime of 750 ns.
• The deep-blue emitter produced electroluminescence with CIE coordinates (0.14, 0.18).
• A high maximum electroluminescence quantum efficiency of 20.7% was achieved, with 20.2% and 17.4% maintained at high luminance.

Conclusions:

• The developed molecular design effectively reduces exciton lifetime in deep-blue TADF emitters.
• The new emitter demonstrates high efficiency and improved performance at high luminance in OLEDs.
• This work offers a promising strategy for efficient deep-blue OLEDs.