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Title: Inverting singlet and triplet excited states using strong light-matter coupling
In organic microcavities, hybrid light-matter states can form with energies that differ from the bare molecular excitation energies by nearly 1 eV. A timely question, given the recent advances in the development of thermally activated delayed fluorescence materials, is whether strong light-matter coupling can be used to invert the ordering of singlet and triplet states and, in addition, enhance reverse intersystem crossing (RISC) rates. Here, we demonstrate a complete inversion of the singlet lower polariton and triplet excited states. We also unambiguously measure the RISC rate in strongly coupled organic microcavities and find that, regardless of the large energy level shifts, it is unchanged compared to films of the bare molecules. This observation is a consequence of slow RISC to the lower polariton due to the delocalized nature of the state across many molecules and an inability to compete with RISC to the dark exciton reservoir.
Authors:
; ; ;
Award ID(s):
1836599
Publication Date:
NSF-PAR ID:
10168330
Journal Name:
Science Advances
Volume:
5
Issue:
12
Page Range or eLocation-ID:
eaax4482
ISSN:
2375-2548
Sponsoring Org:
National Science Foundation
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