Further, using the TDM analysis, we investigated exciton localization and transfer in the studied aggregates. The IPR curves averaged over a swarm of trajectories are shown in Figure . We observe an ultrafast falloff in IPRs, on a fs timescale, for all studied models. This demonstrates the ultrafast exciton localization. In more detail, the initial IPR values are 1.82, 1.83, 2.80, and 3.26 for tetramer 5.5 Å, SAM 5.5 Å, tetramer 3.5 Å, and SAM 3.5 Å, respectively. Thus, the initial exciton is already quite localized for the models with a = 5.5 Å, but is more delocalized for the systems with a = 3.5 Å. The (partial) localization is the result of thermally induced conformational disorder. There is only a very minor difference in the initial IPR values between tetramer 5.5 Å and SAM 5.5 Å, but the difference between tetramer 3.5 Å and SAM 3.5 Å is much larger, 2.80 vs. 3.26, showing a more delocalized exciton for SAM 3.5 Å. This correlates with the difference in conformational flexibility (see Figure ). The value for tetramer 3.5 Å, 2.80, is in good agreement with our earlier TD-lc-DFT results, which yielded IPR of about 2.5-3.1. Further, the IPR curves exhibit an extremely ultrafast initial rise, reaching a maximum at 2 fs, 2 fs, 4 fs, and 6 fs for tetramer 5.5 Å, SAM 5.5 Å, tetramer 3.5 Å, and SAM 3.5 Å, respectively (see the inset in Figure ). The corresponding IPR maximal values are 2.34, 2.23, 3.16, and 3.55. Thus, directly after the excitation, the exciton becomes more delocalized. Interestingly, a similar behaviour was observed in Ref. 36 for the 2-pyridone dimer. The subsequent excited-state dynamics leads to exciton localization. In order to estimate the localization time τ loc , we fitted the IPR curves using the following functions: Further, we calculated the LE and CT measures along the trajectories. These measures averaged over the swarm of trajectories are shown in Figure , for SAM 3.5 Å. At time t = 0, LE ≈ 0.84 and CT ≈ 0.16. Thus, the initial brightest states contain some nonnegligible admixture of CT excitations (for SAM 3.5 Å). Following photoexcitation, LE slightly decreases and CT increases, reaching after about 10 fs values of 0.75 and 0.25, respectively. After oscillating at this level for 90 fs more, LE starts to increase and CT to decrease, reaching at 10 ps LE ≈ 0.99 and CT ≈ 0.01. For the other studied systems LE ≈ 1 and CT ≈ 0 throughout the dynamics (see Figure ).