In view of the almost identical properties of the S/R-enantiomers, the molecules with S-configuration are taken as examples for photophysical property investigation. According to geometrical and electronic structures simulated by theoretical calculation , the HOMOs and LUMOs are basically distributed on carbazole and benzonitrile, respectively, but they show apparent overlaps on the phenyl bridge (Fig. and Supplementary Fig. ). The insufficient separation of HOMOs and LUMOs causes large theoretical energy gaps of 0.84-0.92 eV between the lowest excited triplet (T1) and singlet (S1) states, indicating typical RISC process from T1 to S1 states can hardly occur in these materials. Nevertheless, the energy gaps between high-lying excited triplet (T4-T6) states and S1 state are really small (0.09-0.19 eV), while the energy gaps between T3 and T4 states are quite large (0.42-0.49 eV).