Enhanced Reverse Intersystem Crossing Promoted by Triplet Exciton-Photon Coupling

Area of Science:

• Optics and Photonics
• Materials Science
• Physical Chemistry

Background:

• Polaritons are hybrid light-matter states formed in microcavities, crucial for manipulating excitonic and photonic properties.
• Lower polaritons (LP) have been utilized to lower the energy barrier for reverse intersystem crossing (rISC) from triplet states (T₁), enabling fluorescence via thermally activated delayed fluorescence.
• Previously, spin-orbit coupling between T₁ and the excitonic part of LP was considered the primary mechanism for rISC.

Purpose of the Study:

• To propose and investigate a novel mechanism for rISC promotion in polaritons.
• To demonstrate that light-matter coupling (LMC) between T₁ and the photonic part of LP can drive rISC.
• To explain the experimentally observed enhancement of the rISC process in erythrosine B.

Main Methods:

• Theoretical calculations were employed to model the rISC process.
• The study focused on the LMC between the T₁ state and the photonic component of the lower polariton.
• The mechanism considers the transition dipole moment of T₁ induced by intersystem crossing (ISC).

Main Results:

• The proposed LMC mechanism effectively promotes the rISC process.
• Calculations confirm that this mechanism explains the enhanced rISC observed for erythrosine B.
• This mechanism, previously excluded, offers a new perspective on polariton-enhanced photophysics.

Conclusions:

• Light-matter coupling between T₁ and photons in LP is a significant pathway for promoting rISC.
• This finding broadens the design principles for highly efficient cavity-promoted light-emitting materials.
• The study provides immediate benefits for understanding and developing related experimental phenomena in optoelectronics.