Radical TADF: Quartet-Derived Luminescence with Dark TEMPO

Area of Science:

• Organic electronics
• Quantum technologies
• Photophysics

Background:

• High-spin states in organic molecules are crucial for quantum technologies.
• Current applications are limited by the lack of optical readout via luminescence.
• Photogenerated quartet excitons are a key area of study.

Purpose of the Study:

• To demonstrate a new class of molecules with quartet-derived luminescence.
• To enable optical readout of high-spin states in organic molecules.
• To establish design rules for tuning quartet luminescence.

Main Methods:

• Synthetically appending non-luminescent TEMPO radicals to thermally activated delayed fluorescence (TADF) chromophores.
• Tuning molecular energetics in a series of naphthalimide (NAI) core-based compounds.
• Observing quartet state generation and measuring radical-triplet exchange.

Main Results:

• Demonstrated quartet-derived luminescence in novel organic molecules.
• Established design rules for controlling quartet state energetics and emission.
• Achieved up to 72% photon emission via reverse intersystem crossing from the quartet state in DMAC-TEMPO.
• Showcased a strategy not reliant on luminescent radicals for high-spin state emission.

Conclusions:

• A new design strategy enables quartet-derived luminescence in organic molecules.
• This approach overcomes limitations of optical readout for high-spin states.
• The developed molecules and design rules offer a broad palette for tunable emission colors in organic electronics.