Additionally, the presence of aggregates would explain the fast rate of triplet fusion at high TIPS-Tn concentration. If SF at 300 mM occurs on an aggregated pair of TIPS-Tn molecules, then the triplets are not well separated spatially and can recombine quickly. However, in a dilute solution with no aggregates, in which SF occurs during transient collisions, the molecules may diffuse away before the triplets recombine. Therefore the triplet fusion rate would be lower and a more significant amount of triplets would be observed. We note that the presence of aggregates at 300 mM does not affect the main conclusion of the study by Dover et al., i.e., that the excimer is a trap state rather than an intermediate. However, for the remainder of this study, we revert to the much simpler model shown in Eqs. ( ) and ( ) to describe SF in this system.