The fundamental assumption used in GHTC Hamiltonian (compared to the rigorous quantum electrodynamics Hamiltonian) can be found in Ref. 11 (see Sec. 2.6.1) as well as in Refs. 14-16. The excitonic Hamiltonian is Ĥex = N -1 n=0 (hω ex + λ)σ † n σn , where σ † n = |e n ⟩⟨g n | and σn = |g n ⟩⟨e n | are the raising and lowering operators for the exciton on the n th molecule, respectively. Further, |g n ⟩ and |e n ⟩ are the ground state and excited state of the n th molecule, respectively, hω ex = E e -E g is the excitation energy between the ground and excited states, and λ is the reorganization energy (that give rise to Stokes shift in linear spectra) due to exciton-phonon coupling. The Ĥex-b + Ĥb terms further describe interactions between exciton and phonon bath, with details provided in the Supporting Information.