Molecular Locking in Triplet Sensitization Amplifies Circularly Polarized Luminescence

Area of Science:

• Materials Science
• Photochemistry
• Organic Chemistry

Background:

• Chiral organic molecules with circularly polarized luminescence (CPL) are promising for applications, but limited by luminescence efficiency and dissymmetry factors (g_lum).
• Achieving high g_lum is challenging due to parity selection rules for electric and magnetic dipole moments in chiral systems.

Purpose of the Study:

• To overcome molecular limitations in dissymmetry factors for CPL.
• To develop a triplet sensitization photon upconversion system for amplifying CPL.
• To investigate the mechanism behind enhanced CPL through triplet sensitization.

Main Methods:

• Designed a triplet sensitization photon upconversion system using non-toxic copper indium disulfide (CuInS₂) quantum dots (QDs) as photosensitizers.
• Investigated QD-sensitized triplet fusion processes and direct photoexcitation.
• Performed modeling and first-principles calculations to understand the origin of enhanced g_lum.

Main Results:

• Achieved a 43-fold amplification of CPL in the QD-sensitized triplet fusion process compared to direct photoexcitation.
• Obtained a high green-to-blue upconversion quantum efficiency of 12.7 ± 0.19%.
• Demonstrated significantly improved dissymmetry factors (g_lum) for QD-sensitized upconversion CPL compared to molecular photosensitizers.

Conclusions:

• The QD-sensitized triplet sensitization strategy effectively amplifies CPL.
• The enhanced g_lum arises from structural rearrangement of the chiral emitter during ultrafast triplet energy transfer.
• This work offers a new strategy and mechanistic understanding for CPL amplification.