Red OLED with efficiency of 25.6% at 10,000 cd m^-2 based on selenium embedding multiple resonance framework

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Multiple resonance thermally activated delayed fluorescence (MR-TADF) materials offer narrowband emission and high efficiency, crucial for advanced displays.
• Red MR-TADF organic light-emitting diodes (OLEDs) face significant efficiency roll-off due to slow reverse intersystem crossing (RISC).

Purpose of the Study:

• To develop efficient red MR-TADF emitters that overcome the efficiency roll-off limitation.
• To investigate a novel selenium-embedded framework for enhanced RISC rates and performance in OLEDs.

Main Methods:

• Synthesis and characterization of a novel selenium-embedded red MR emitter (tFSeBN).
• Fabrication and testing of OLED devices utilizing the tFSeBN emitter.
• Evaluation of device performance, including external quantum efficiency (EQE) and efficiency roll-off at various luminance levels.
• Assessment of tFSeBN as a sensitizer in hyperfluorescent OLEDs.

Main Results:

• The tFSeBN emitter exhibits red emission at 607 nm with a record-high RISC rate of 7.5 × 10^5 s^-1.
• The corresponding OLED achieved a maximum EQE of 34.7% and maintained high EQE values (31.0% at 1000 cd/m^2, 25.6% at 10,000 cd/m^2), demonstrating ultra-low efficiency roll-off.
• As a sensitizer, tFSeBN enabled pure-red emission (CIE: (0.70, 0.30)) with high EQE and suppressed roll-off in hyperfluorescent OLEDs.

Conclusions:

• The selenium-embedded MR framework effectively accelerates RISC, addressing the critical efficiency roll-off issue in red OLEDs.
• tFSeBN serves as both a high-performance emitter and an efficient sensitizer, offering a viable alternative to noble-metal-sensitized systems.
• This approach provides a promising pathway for developing next-generation red OLEDs for ultra-high-definition displays.