and 4CzIPN (Figures ), with the T1 values provided in Table . The unproductive for the determination of ET. We thus estimated the ET from the difference between the experimentally determined S1 energy at RT and the DEST obtained at 77K. The ΔEST of these PCs can be inferred from the difference in energy of the onsets of the steadystate and millisecond-gated emission spectra at 77 K (Table ). Since the S1 state of TADF compounds typically has greater CT character than the T1 state, the S1 state will be stabilized to a greater degree than the T1 state in polar solvents, meaning that ΔEST values will decrease in polar solvents compared to the value obtained at 77 K. Thus, the true value of ET will be lower in energy than the one estimated by us. Using our method, the ΔEST was determined at 77 K to be 0.03 eV for 4CzIPN, resulting in an estimated ET value of 2.62 eV in MeCN. The experimentally determined/estimated ET values of the PCs are collated in The excited-state redox potentials, E*ox and E*red, which are themselves dependent on the E0,0