Fig. 4: Fluence Dependent Pump-probe Spectroscopy of Single and Connected Aggregates.

Dynamics of the pump-probe excited-state absorption feature at 580 nm are shown as a function of delay time for (a) connected aggregates (average of n = 10 replicates taken on the same sample for all fluences; shaded error bars are 1 standard error in the mean) all taken on the same sample for all fluences; shaded error bars are 1 standard error in the mean as are error bars on individual data points) and inset data for connected aggregates is collected separately: n = 7 replicates (10 nJ, 22 nJ), n = 5 replicates (60 nJ), n = 7 replicates (74 nJ), n = 5 replicates (98 nJ), n = 7 replicates (118 nJ), n = 4 replicates (130 nJ) (b) isolated aggregates (average of n = 40 replicates (11nJ), n = 20 replicates (42nJ), n = 10 replicates (72 nJ, 80 nJ), n = 7 replicates (100 nJ, 112 nJ), n = 6 replicates (130nJ). In the inset of a and b, the fluence dependence of the signal is shown. It is observed that the magnitude of the signal increases quadratically with pump-fluence, indicating the multi-exciton regime at higher fluences for both aggregate types. All traces are normalized to 10 ps. Source data for a and b are provided as a source data file. c A schematic showing the difference between connected and isolated aggregates’ dynamics: in connected aggregates, exciton diffusion allows excitons of many different spatial phases to meet, whereas in isolated aggregates, the excitons remain on the same quantum site without annihilating.