In this section all samples consist of 10 mM annihilator + 25 µM 4CzBN if not stated otherwise (1 mM for 2PI and TIPS-Naph). Time-resolved emission measurements were performed for each annihilator at different excitation intensities, and the measurements were fitted to normalized data using Equation S6 (Equation 2 in the main text). A global fitting procedure was used where b was allowed to vary between measurements, but tT was shared globally.