Figure 4.

Triplet identification. (a) Integrated decay kinetics from all species, at the peak of PIA, following excitation at 2.3 eV. All aggregates (solid) show an enhancement of the final state lifetime of 5 orders of magnitude, relative to the monomer (dashed). (b) Comparison of the TA signal at 100 ns for all five aggregates reveals the same PIA signature in each, combined with a GSB related to the UV–vis absorption. The final state must be the same in all aggregates. (c) Comparison of the absorption edge (dashed) and long-lived TA signal (solid) of monomer AXT following triplet sensitization (green) and aggregate II. The similarity of shape confirms the assignment of the long-lived aggregate state to triplets, produced via singlet fission.