Energy transfer problem in extended aggregates involves multiple electronic states and vibrational modes. In this multidimensional problem, there is often limited to no knowledge of which vibrational motions promote energy transfer against vibrational motions which are spectators in the process. Additionally, capturing the role of vibronic coupling in enhancing energy/charge transport requires explicit quantum treatment of several vibrational modes, which rapidly scales the calculation costs. This often necessitates approximations to reduce the basis set size. We show that a commonly used approximation in exact numeriacal diagonalization approaches completely fails to capture vibronic enhancement of energy/charge transport. Instead we propose an alternative effective-mode approach which - 1. reduces the dimensionality while exactly treating vibronic coupling, 2. identifies reaction coordinates, motions along which maximally promote energy transfer in extended molecular aggregates. We exemplify our approach to propose a novel design principle of trap-mediated energy transport. Modulating trap behavior from an excitation 'trap' to a 'shuttle' for energy transfer can be a potential switch to control vibronicaly enhanced energy transfer between uncoupled donor-acceptor sites. Figure: Trap-mediated energy transfer controlled through vibronic resonance. Uncoupled donor-acceptor sites do not exchange energy such that a 'trap' site will receive all the excitation from the donor without transferring it to the acceptor. We show that certain vibrational motions can convert the `trap' to a `shuttle' for promoting donor-acceptor energy transfer, even if donor and acceptor are uncoupled. This behavior is controllable through a vibronic resonance. Adapted from J.Chem.Phys. Communication 2021, Sanjoy Patra et al.

Trap-mediated energy transfer via vibronic resonance

ACS Fall 2021

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