The oscillator strengths of all exciplexes significantly decrease compared to that of the monomers and are quite sensitive to their stacking conformation, (Table ), which could be referred to as the aggregation-caused quenching (ACQ) effect of H-aggregates. As illustrated in Figure , compared with the TDM of the first LE state of C22 and PC113 (thin red and green arrows), the TDMs of dimers (thick cyan arrows) are significantly reduced. This can be explained by two reasons: (1) the TDMs of the monomer LE states (thick red & green arrows) make an obtuse angle and cancel each other, and (2) the involvement of CT states reduces the dimer excitation's LE character and oscillator strength (see Table ), as found in previous studies about homodimer excitations. To test whether the redshift is universal for all conformations and gain insights into the excited state intermolecular interaction, we performed thorough PES scans of the C22-PC113