Here 𝑘 𝑆 𝑡𝑜𝑡 and 𝑘 𝑇 𝑡𝑜𝑡 are defined as the sum of all rate constants of the unimolecular processes (i.e., not including the bimolecular processes discussed in sections below) occurring from the singlet and triplet state, respectively. 𝑘 𝑆 𝑡𝑜𝑡 and 𝑘 𝑇 𝑡𝑜𝑡 , as well as the product of the rate constants of ISC and RISC (𝑘 𝐼𝑆𝐶 𝑘 𝑅𝐼𝑆𝐶 ) can be extracted by considering the ratio of fluorescence intensity between the two individual decays as measured by time-correlated single photon counting, according to equations 3-5 (see SI). This ratio should be measured with sufficient data points on the prompt decay to ensure the ratio is reliable, and therefore it is best to do one measurement that captures the entire decay and one that mostly captures the prompt decay, see SI.