To quantify the amounts of SF occurring in the 8 mM solutions, we deconvoluted the TA data to determine S 1 and T 1 basis spectra, i.e. the contribution per mole of chromophores in the S 1 and T 1 states, respectively, to the TA spectrum. This process is described in detail in Sec. S3 of the supplementary material. Briefly, the S 1 basis spectrum was determined from the expected concentration of excitons generated by the pump pulse and the TA spectrum at early times, before significant exciton decay, ISC, or SF occurs (supplementary material Sec. S3.1.1 for TIPS-Pn and S3.2.1 for TIPS-Tn). The triplet basis spectrum was determined by subtracting the singlet component from the 8 mM TA spectrum at 8 ns. The true magnitude of the S 1 component at 8 ns is unknown, but we can determine an upper and lower limit on the amount present, leading to upper and lower bounds on the T 1 basis spectrum (supplementary material Sec. S3.1.2 for TIPS-Pn and S3.2.2 for TIPS-Tn). The full 8 mM TA spectrum was then fit to a linear combination of the S 1 and T 1 basis spectra, ε S 1 (λ ) and ε T 1 (λ ), at each delay time, t, using