A general structural decoupling strategy toward ultra-long blue circularly polarized room-temperature phosphorescence

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Circularly polarized room-temperature phosphorescence (CP-RTP) materials are crucial for 3D displays and information encryption.
• Achieving high-performance blue CP-RTP is challenging due to the trade-off between triplet energy (E_T) and spin-orbit coupling (SOC) efficiency.
• Conventional methods often result in red-shifted emission due to heteroatom incorporation that stabilizes excited states.

Purpose of the Study:

• To develop a new molecular design strategy for high-energy, long-lived blue CP-RTP materials.
• To overcome the inherent E_T-SOC trade-off in organic chiroptical materials.
• To enable efficient blue emission by preserving high triplet energy.

Main Methods:

• Proposed a "structural decoupling" strategy using a non-conjugated methylene (-CH₂-) bridge.
• This bridge connects chiral n-electron units to a π-conjugated backbone, interrupting electronic conjugation.
• Utilized D/L-4,4 omino'-biphenylalanine (D/L-BPAla) as a model system and doped it into PVA films.

Main Results:

• The structural decoupling strategy successfully preserved the high triplet energy of the biphenyl unit.
• Achieved blue CP-RTP emission at 475 nm with a long lifetime of 2.91 s.
• Demonstrated a phosphorescence quantum yield of 9.10% and an asymmetry factor (g_lum) of 3.75 × 10^-3.

Conclusions:

• The proposed strategy effectively shifts excited-state character to high-energy π → π*, enabling blue emission.
• This method maintains efficient SOC through spatial proximity, overcoming the E_T-SOC trade-off.
• Provides a versatile blueprint for designing advanced organic chiroptical materials with high energy and long lifetimes.