In order to give a quick prediction of the OEEF effect, we summarize three possible interaction modes of OEEFs in Scheme 3. For simplicity, the one-dimensional situation is considered. In actual situations, the direction of the difference dipole moment can be chosen to simplify the problem and maximize the effect of OEEFs. Assuming that the ground state dipole moment (μ 0 ) has a magnitude of 1.0 D, three different situations can be envisioned. In the first two cases, the excited state dipole moment (μ 1 ) is positive. In case 1, μ 1 is smaller than μ 0 , while in case 2, μ 1 is larger than μ 0 . In the last case, the direction of μ 1 is opposite to that of μ 0 . Without loss of generality, the value of μ 1 can be assumed to be 0.5 D, 2.0 D and -1.0 D, in cases 1, 2 and 3, respectively. Consequently, the value of the difference dipole moment ∆μ = μ 1 -μ 0 , can be obtained as -0.5 D, 1.0 D, and -2.0 D in cases 1, 2 and 3, respectively. When a positive field is applied, the field stabilizes the ground S 0 state due to the alignment of its dipole moment. Similarly, the positive field will lower the energy of the S 1 state in cases 1 and 2, but with different magnitudes due to their different dipole moments. In case 1, the stabilization effect on the S 1 state is weaker than the S 0 state. As a result, the emission energy E F is increased, and the emission maximum λ F is blueshifted by the positive field. In case 2, the situation is reversed, and the stabilization effect on the S 1 state is stronger than the S 0 state. Consequently, E F is decreased, and λ F is red-shifted by the positive field. Notably, the situation of LFOH or HFOH discussed above is consistent with case 2. In case 3, a positive field destabilizes S 1 state due to its negative dipole moment. Thus, the energy gap between the S 0 state and S 1 state (E F ) is greatly enlarged due to the decrease of E 0 and the simultaneous increase of E 1 . Accordingly, the wavelength will be largely blue-shifted by the positive field in case 3. A negative field leads to the exact opposite effect in all three cases. According to Scheme 3, the above analysis can be simplified by using difference dipole moment ∆μ, which can be obtained experimentally. A field along the same direction as ∆μ decreases E F and redshifts the spectrum, whereas a field in the opposite direction increases E F and blueshifts the spectrum.