Quantum Master Equation Approach to Singlet Fission Dynamics of Realistic/Artificial Pentacene Dimer Models: Relative Relaxation Factor Analysis

Abstract

The singlet fission (SF) dynamics of realistic/artificial pentacene dimer models are investigated using the quantum master equation method in order to obtain new insight into the SF dynamics and its rational design guidelines. We comprehensively clarify the effects of the energy offsets of diabatic Frenkel exciton (FE) and charge transfer (CT) exciton states to the double-triplet (TT) exciton state, excitonic couplings, and state-dependent vibronic couplings on the exciton population dynamics using relative relaxation factors (RRFs) between the adiabatic exciton states. As shown in previous studies, efficient sequential/superexchange CT-mediated SF is observed in the energy level matching region (E(TT) – E(FE) < 0). On the other hand, it is predicted that almost the perfect energy level matching (E(TT) – E(FE) ∼ 0) causes the significant reduction of TT yields though exhibits remarkably fast SF rates, when the corresponding adiabatic double-triplet (TT′) and Frenkel exciton (FE′) states are near-degenerat...