Here, I is intensity, E is excitation energy, N s is the number of selected snapshots, E i,α and f i,α are the TD-DFT excitation energy and oscillator strength, respectively, for the S 0 → S i transition, for snapshot α, and σ is a broadening parameter (σ = 0.05 eV in this work). For each selected snapshot we also calculate the spectra of four monomers forming the aggregate (to calculate the broadened spectrum of the monomer, 4N s instead N s is used in the denominator of eq. ( )).