For the ensemble absorption and emission lineshapes, the average values of the vertical excitation and deexcitation energies are aligned with the experimental lineshape maxima. For vibronic spectra, we aligned the lineshape maxima, except for more jagged spectra, where averaged band maxima were used to determine alignment. This averaging procedure selects the peaks within 80% of the first maximum and then computes the average energy of these peaks. For all computed lineshapes, the applied energy shift is given in the main manuscript, and the unshifted lineshapes are shown in the Supplementary Material, Figure .