The excited states of Cz-BDF (Fig. , right) bear resemblance to those of Cz-BDT (Fig. ). At the S 0 geometry two locally excited triplet states are found before S 1 , which is also locally excited and dark similarly to Cz-BDT and Cz-AQ. S 2 is found to be a bright CT state at an excitation energy of 2.73 eV, which is almost equivalent to Cz-BDT. In addition, two triplet nπ * states (T 3 and T 4 ) and another singlet CT state (S 3 ) is found. Optimisation of S 1 slightly lowers its energy (from 2.47 eV to 2.30 eV) while retaining its local character. The other states remain largely unaffected when compared between the S 0 and S 1 geometries. However, it is noteworthy that the gap between S 1 and S 2 becomes 0.51 eV after optimisation. A dark S 1 state along with a large gap to S 2 indicates that any coupling between the states is expected to be small and Cz-BDF is expected to be at most weakly emissive, similarly to Cz-BDT. Optimisation of T 1 slightly stabilises the energy of this state inducing an adiabatic singlet-triplet gap of 0.63 eV. Otherwise, the states remain largely unaffected.