show that the dimer's fluorescence energy is always lower than both of its monomers regardless of its conformations, with its oscillator strength also decreasing. This is because dimer S1 energy never exceeds the lowest monomeric non-adiabatic state, with the further redshift mainly caused by the superexchange effect. The TDM cancellation effect and the CT state's contribution both reduce the total oscillator strength and cause the ACQ effect of asphaltene dimers.