Highly Efficient Circularly Polarized Electroluminescence Based on a Thermally Activated Delayed Fluorescence...

Area of Science:

• Organic electronics
• Photonic technologies
• Materials science

Background:

• Circularly polarized electroluminescence (CPEL) is crucial for advanced technologies but faces challenges in device efficiency (EQE) and circular polarization intensity (gEL).
• Traditional chiral emitters have limited efficiency, and phosphorescent emitters often use rare metals.
• Thermally activated delayed fluorescence (TADF) offers high efficiency but integrating chirality remains difficult.

Purpose of the Study:

• To develop a comprehensive strategy for simultaneously enhancing EQE and gEL in CPEL devices.
• To overcome the limitations of existing chiral emitters by integrating TADF mechanisms.
• To explore diverse chiral structures for efficient CPEL applications.

Main Methods:

• Incorporation of TADF as a core mechanism to harvest triplet excitons via reverse intersystem crossing (RISC), boosting EQE.
• Design and synthesis of diverse chiral structures, including small molecules, polymers, and ionic systems, to amplify gEL.
• Fabrication and characterization of circularly polarized organic light-emitting diodes (CP-OLEDs) and circularly polarized light-emitting electrochemical cells (CP-LECs).

Main Results:

• Achieved high EQE by leveraging TADF and RISC for full exciton utilization.
• Significantly amplified gEL values through various chiral structures, including supramolecular assemblies, without compromising radiative efficiency.
• Demonstrated the first intrinsic TADF-driven CP-OLEDs, chiral TADF polymers, and chiral TADF ionic salts for CP-LECs.

Conclusions:

• The developed strategy provides a holistic solution to enhance both EQE and gEL in CPEL.
• The integration of TADF with advanced chiral structures offers a promising pathway for efficient circularly polarized light sources.
• This work lays the foundation for future advancements in CPEL for next-generation photonic technologies.