The PL decays of the three emitters in toluene under degassed and aerated conditions were measured using time-correlated single-photon counting (TCSPC, Figure ). There is only a single decay component (monoexponential) observed for all three compounds, with lifetimes, tp, of 4.6 ns for TPAPyAP, 5.6 ns for TPAPyBP and 7.2 ns for TPAPyBPN. While there is no longlived TADF emission observed, this may be completely quenched by nonradiative decay in solution; a phenomenon shown in some previously reported TADF compounds, especially for TPA-based TADF emitters. The S1 and T1 energies of the three emitters were elucidated from the onsets of the respective fluorescence and phosphorescence spectra determined in frozen toluene at 77 K (Figure , Table ). The S1 energies of TPAPyAP, TPAPyBP and TPAPyBPN, are 2.64 eV, 2.43 eV, and 2.38 eV, while the T1 energies are 2.34 eV, 2.23 eV, and 2.21 eV, respectively. The phosphorescence spectra of all three compounds are structured, and each is assigned from the TDA-DFT calculations as a mixed locally excited triplet ( 3 LE) state of the acceptor and 3 ICT state (Figure ). The ΔEST values of TPAPyAP, TPAPyBP and TPAPyBPN are 0.30 eV, 0.20 and 0.17 eV, respectively, which, though smaller than the calculated values, nonetheless mirror the trend predicted from the theoretical study. Similar to the other TPA-based TADF emitters, these three compounds also have large ΔEST in solution, yet TADF is observed in the solid state.