Symmetry-Breaking Triplet Excited State Enhances Red Afterglow Enabling Ubiquitous Afterglow Readout

Area of Science:

• Photophysics
• Organic Chemistry
• Materials Science

Background:

• Molecular vibrations typically deactivate luminescence.
• Designing molecules with motion that enhances luminescence is a potential strategy.
• Room-temperature phosphorescence (RTP) is a desirable luminescence property.

Purpose of the Study:

• To investigate the role of molecular motion in enhancing luminescence.
• To explore symmetry-breaking molecular motion in donor-π-donor chromophores for red persistent RTP.
• To develop new materials for advanced anti-counterfeiting technologies.

Main Methods:

• Synthesis of donor-π-donor conjugated chromophores.
• Deuteration of the chromophore to study isotopic effects.
• Measurement of red persistent room-temperature phosphorescence (RTP) yield and lifetime.
• Dynamic calculations of the phosphorescence rate constant (kₚ).

Main Results:

• The deuterated donor-π-donor chromophore exhibited efficient red persistent RTP with a 21% yield and 1.6 s lifetime.
• Symmetry-breaking molecular motion was identified as a key factor enhancing RTP.
• Calculations showed this motion selectively facilitates phosphorescence without increasing nonradiative decay.

Conclusions:

• Symmetry-breaking molecular motion can be a powerful design principle to enhance RTP.
• Efficient red persistent RTP enables long-wavelength excitation and bright-light afterglow detection.
• These findings significantly expand the potential of RTP materials in anti-counterfeiting applications.