We next determined the singlet/triplet (S1/T1) energies of both emitters in 2-MeTHF glass at 77K (Figure ). The S1/T1 energies are 2.48/2.27 eV for 3TPA-DiKTa and 2.17/1.95 eV for 3DPA-DiKTa, resulting in small DEST values of 0.21 eV for 3TPA-DiKTa and 0.22 eV for 3DPA-DiKTa. These values are almost identical to that of DiKTa (~ 0.20 eV) and its derivatives. There is a notable small degree of positive solvatochromism observed for 3DPA-DiKTa (Figure ), which is characteristic of MR-TADF compounds. There is a more pronounced positive solvatochromism for 3TPA-DiKTa, consistent with a more significant admixture of CT character to the SRCT emissive excited state. Full-width at half-maximum; c Photoluminescence quantum yield of thermally evaporated thin films, measured using an integrating sphere, under N2 at lexc = 340 nm. Measured at lexc = 379 nm and 300 K under vacuum; e Obtained from the onset of the prompt spectrum (1-100 ns) at 77 K. f Obtained from the onset of the delayed spectrum (1-8.5 ms) at 77 K (lexc = 343 nm). g DEST = E(S1) -E(T1).