Highly Horizontal Oriented Tricomponent Exciplex Host with Multiple Reverse Intersystem Crossing Channels for...

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters offer potential for wide color-gamut displays and eye-protection lighting.
• Existing MR-TADF devices suffer from efficiency roll-off due to inefficient reverse intersystem crossing (RISC) and long exciton lifetimes.
• Exciton quenching and inefficient upconversion of nonradiative triplet excitons limit the performance of current MR-TADF OLEDs.

Purpose of the Study:

• To propose a novel device concept using a highly efficient tricomponent exciplex as a host for MR-TADF OLEDs.
• To enhance the reverse intersystem crossing (RISC) process and reduce exciton quenching.
• To achieve high external quantum efficiency (EQE) and minimize efficiency roll-off in MR-TADF OLEDs.

Main Methods:

• Fabrication of organic light-emitting diodes (OLEDs) utilizing a novel tricomponent exciplex (p-PhBCzPh: PO-T2T: DspiroAc-TRZ) as a host material.
• Investigation of photoluminescence quantum yield, emitting dipole orientation, and RISC rate constants of the tricomponent exciplex.
• Doping the tricomponent exciplex host with sky-blue and pure-green MR-TADF emitters to evaluate device performance.

Main Results:

• The tricomponent exciplex demonstrated significantly improved photoluminescence quantum yield, emitting dipole orientation, and RISC rate compared to binary exciplexes.
• A record-breaking external quantum efficiency (EQE) of 30.4% was achieved for the tricomponent exciplex-based OLED.
• Maximum EQEs of 36.2% (sky-blue) and 40.3% (pure-green) were recorded, with ultralow efficiency roll-off (26.1% and 30.0% at 1000 cd m⁻²).
• A blue-hazard-free warm white OLED was developed using a double-emission-layer structure, achieving an EQEmax of 30.3% and stable spectra.

Conclusions:

• The proposed tricomponent exciplex host effectively enhances RISC and suppresses exciton quenching, leading to high-performance MR-TADF OLEDs.
• This strategy overcomes the limitations of efficiency roll-off in conventional MR-TADF devices.
• The developed technology holds promise for advanced display and lighting applications, including eye-safe lighting solutions.