Tellurophene-Induced Triplet-Singlet Spin-Flip Acceleration: An Advanced Design for Narrowband Organoboron Emitters...

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Multi-resonance (MR) emitters are crucial for wide-color-gamut organic light-emitting diodes (OLEDs), offering high efficiency and color purity.
• Conventional MR-type thermally activated delayed fluorescence (MR-TADF) emitters face efficiency roll-off at high brightness due to slow reverse intersystem crossing (RISC).

Purpose of the Study:

• To design and synthesize novel MR-TADF emitters that overcome efficiency roll-off by accelerating the RISC process.
• To investigate the impact of incorporating tellurium (Te) into MR-TADF emitters to enhance spin-orbit coupling and improve device performance.

Main Methods:

• Synthesized Te-containing MR-TADF emitters by tethering dibenzo[b,d]tellurophene to a MR skeleton.
• Characterized the photophysical properties, including RISC rates and emission bandwidths.
• Fabricated and tested OLED devices using the novel Te-containing emitters.

Main Results:

• Achieved fast RISC rates up to 2.8 × 10^6 s^-1 and narrow emission bandwidths of 23-25 nm.
• Demonstrated high external quantum efficiencies (EQEs) up to 35.3% in OLEDs.
• Significantly reduced efficiency roll-off, maintaining high EQEs (32.2% at 10^3 cd m^-2, 25.4% at 10^4 cd m^-2).

Conclusions:

• Te-containing MR-TADF emitters effectively accelerate RISC through enhanced spin-orbit coupling.
• These novel emitters show great potential for next-generation OLEDs requiring high efficiency and brightness.
• The incorporation of Te is a promising strategy for developing high-performance OLED materials.