Reviewing Figures and, we find that both molecules retain significant adiabatic singlet-triplet gaps, even when solvation effects are accounted for. Thus, the singlet-triplet gap does not serve as a suitable figure of merit to differentiate between the two molecules. On the other hand, a clear difference is observed in terms of excited-state character of the optimised S 1 state. This state becomes a dark locally excited state for Cz-BDT whereas it becomes a bright symmetry-broken CT state for Cz-AQ. The enhanced optical brightness is certainly beneficial for luminescence while also enhanced CT agrees with the underlying design strategy. Both phenomena explain the enhanced performance of Cz-AQ. The difference in state character is reflected by the more planar structure of Cz-BDT in its ground and excited states when compared to Cz-AQ. This planar structure along with shorter bond lengths is an indication of enhanced conjugation between BDT and Ph when compared to AQ and Ph. The difference can, in part, be understood by the reduced steric repulsion between BDT and Ph but electronic effects most probably also play a role as Cz-AQ is, indeed, able to planarise as seen for the T 1 minimum.