The 6 ps component is unique to Cl-GNR samples and has not been observed in Cl-GQDs. We considered the possibility that this kinetic component is associated with the recombination of free charge carriers formed upon photoexcitation. Previous reports indicate that the exciton binding energies in nanographenes range from 0.1 to 0.6 eV for GQDs 6,7,60 and 0.5 to 2.5 eV for GNRs. Furthermore, time-resolved microwave experiments show that the free carriers are formed in nanographenes when excitation pulse energies exceed the exciton binding energy and that these carriers recombine on picosecond timescales. To explore whether our 6 ps decay is associated with recombination of free charge carriers, we performed TA experiments using different excitation pulse energies (Figure , SI). If this component arises due to charge carrier recombination, it will disappear from the spectra obtained at low excitation energies, because the excitation pulse is not energetic enough to dissociate excitons into free carriers. Our data clearly show that the 6 ps component does not disappear from the transient decays, even when a very low energy excitation pulse (λexc=600 nm) is used, indicating that this process is not associated with free charge-carriers. A more plausible origin of the 6 ps component is the excited-state decay of aggregated Cl-GNR. Based on the observed aggregation of nanoribbons in 2D excitation/emission spectra of Cl-GNR, it is quite likely that the observed transient data contain contributions from both isolated and aggregated ribbons. Since the aggregated ribbons are expected to exhibit short excited-state lifetimes, 8,51,52,62 the 6 ps component is assigned to the excited states of aggregated Cl-GNRs (Figure ). This assignment is consistent with our observations of H-GNR which exhibits rapid decay on the single to tens of picoseconds timescale. The observed formation of long-lived triplet states in Cl-GNR is quite unique. All previous studies of graphene nanoribbon photophysics report relatively short-lived singlet excited states with lifetimes on the order of ~100 ps. The observed 106 μs lifetime is excellent for potential photocatalysis applications where long-lived excited states are required to provide sufficient time for useful chemical reactions to take place. The charge-transfer character of H-GNR excited states (Figure ) is a direct consequence of electron accepting properties of bipyrimidine moieties and enables spatial separation of electrons and holes within the exciton, which is useful for photoinduced electron transfer processes that initiate most photocatalytic reactions. We expect similar charge-transfer states in Cl-GNR given the similarities between H-GQD and Cl-GQD difference density plots (Figure , SI). In addition to exhibiting long-lived triplet excited states, Cl-GNR absorb very well in the visible range (Figure ), making them excellent light-harvesting chromophores. Based on the computational results presented here, we speculate that the triplet states in Cl-GNR are charge-transfer in character and, therefore, well-suited for application in photocatalysis. Furthermore, the observed optical bandgap in Cl-GNR (~2 eV) is ideal for solar fuel applications, such as photochemical water splitting or CO2 reduction, as it provides enough energy for required reaction thermodynamics (for example, 1.23 eV for solar water splitting) and for associated kinetic overpotentials (usually few hundred meVs). Finally, the bipyrimidine edges on Cl-GNR can serve as coordination sites for molecular transition metal catalysts for future applications in photocatalysis, as many of reported catalysts utilize polypyridyl ligands. Given all these arguments, the photophysical findings presented here illustrate the potential of Cl-GNR for applications in solar energy conversion systems.