From the photophysical investigation, we have demonstrated that the PL emission is largely similar for each of the three compounds, with the presence of the additional low energy band in 4TABN1 that we ascribe to an excimer or exciplex-like species. We finally employed DFT calculations and time-dependent DFT calculations within the Tamm-Dancoff approximation (TDA-DFT) using the PBE0 functional with the 6-31G(d,p) basis set to model the optoelectronic properties of the three emitters (Figure , Table and S4). This protocol has been widely applied by us and others to accurately model the optoelectronic properties of TADF emitters. In expanding the structure from one benzonitrile acceptor to two and three acceptor units there is a progressive stabilization of the HOMO energy from -5.17 eV in 4TABN1 to -5. In line with decreasing ΔE, there is stabilization of the S1 state from 3.27 eV to 3.11 eV and 3.05 eV for 4TABN1, 5TABN2 and 6TABN3, respectively. This decreasing S1 energy is not reflected in the experimentally obtained absorption spectra (calculations that incorporate a toluene solvent corroborate those conducted in the gas phase as shown in Table . We ascribe the discrepancies due to the large conformational degrees of freedom in this series, especially in the larger molecules, while the calculations focus only on a fixed geometry. Across the series an increase in oscillator strength is apparent from 0.25, 0.41 and 0.56 for 4TABN1, 5TABN2 and 6TABN3, respectively, and is expected owing to increasing conjugation in the ground state geometry with increasing size. This is in line with the increasing experimental ε values observed in toluene (vide supra) and are comparable to oscillator strengths in toluene (Table ). Regarding the properties of the intermediate triplet states, the higher-lying triplet states (T3-T4) are stabilized more significantly compared to S1 along the series (Table ). For example, the energy of T3 changes from 3.29 eV to 2.88 eV and 2.85 eV along the series, with T3 being more than 200 meV below S1 for 5TABN2 and 6TABN3, respectively. Given such a large and unambiguous energetic difference between S1 and T3, we nevertheless expect the predicted higher-lying triplet states to play a role as intermediate triplet states in 5TABN2 and 6TABN3, even when the DFT calculations predict greater conjugation in the oligomers than experimentally observed. The calculations show that the number of intermediate triplet states increase along the series (Figure ), with 1, 2, and 3 intermediate triplet states present in 4TABN1, 5TABN2, 6TABN3, respectively. Their presence would support the trend in experimentally determined kISC. However, having intermediate triplet states alone is not sufficient to explain the enhanced TADF in 5TABN2 and 6TABN3. An efficient SOC between the singlet and triplet manifolds is enabled by states of different symmetry and electronic configuration. This means that a strong SOC can be enabled if the transition between singlet and triplet states involves a change of molecular orbital type. We therefore quantified the degree of CT versus LE character of the excited states using the ϕS metric, 41 wherein we assign an excited state with a ϕS = 1 as being locally excited (LE), a ϕS = 0 as charge transfer (CT) and intermediate values as mixed LE/CT states along with the predicted SOC values. For each of the emitters both the T1 and S1 states are predicted to be of mixed CT/LE character (ϕS =0.5 -0.6, see Table and Figures ), consistent with the photophysical investigation. For 4TABN1, the higher-lying triplet states, T2 -T4, are all LE with ϕS > 0.75, while for 5TABN2 and 6TABN3