Figure 5.

Energy diagrams illustrating TADF with natural transition orbitals (NTOs) for each state on optimized S₁ excited-state geometry of 1a and 1c from TD-DFT computations with the solvation model cLR-PCM using DCM as a solvent. PF = prompt fluorescence, DF = (thermally activated) delayed fluorescence, ISC = intersystem crossing, RISC = reverse intersystem crossing, ΔE_ST = S₁ energy – T₁ energy, ¹CT = singlet charge-transfer state, ³CT = triplet charge-transfer state, ³Fl = local triplet excitation state at the fluorene donor unit, and ³A = local triplet excitation state at the acceptor unit. Contours in NTOs are drawn at ± 0.04 (e/bohr³)^1/2.