Several recent large-scale computational screening studies revealed that it is challenging to reconcile robustly negative or small positive singlet-triplet gaps ΔST with significant oscillator strengths of the S1-S0 transition. The reason for the tight correlation of singlet-triplet gaps and oscillator strengths is well understood. Singlet-triplet near-degeneracy requires an exceptionally small exchange integral which can be achieved with spatially non-overlapping HOMO and LUMO. The lack of orbital overlap necessarily also results in a small S1-S0 transition dipole moment and oscillator strength. Unsurprisingly, this general trend also is encountered in the CBN ribbons. Nevertheless, it has been found in the present study that the CBN_1-4 ribbon, for example, combines a negative ΔST with an oscillator strength of 0.3.