To further understand the origin of the trend, we analyzed the excited state compositions of the parallelly stacked C22-X and PC113-X series (Figure ). Overall, the exciton tends to localize more on the monomer with the lower S1 energy, which can be explained by the CI vector shown in Eq. ( ). For the C22-X series, the contribution from monomer X's LE state gradually decreases from 100% to 0% as X's fluorescence energy increases, while the C22 LE for the correspondence between monomer ID and names used in this section.