Simulation of photoexcitation dynamics in conjugated polymer using Ehrenfest method with configuration interaction singles

Abstract

Ehrenfest method is commonly used for simulating photoexcitation dynamics in conjugated polymers. However, due to the expensive computational cost, the calculation of electronic excited states for long conjugated polymer chains in Ehrenfest simulations is still at the level of Hartree–Fock approximation. Here, we develop an approach to perform Ehrenfest simulations in terms of configuration interaction singles (CIS) that is beyond the Hartree–Fock approximation. With this approach, we simulate the relaxations of various photoinduced excited states in a single polymer chain. The simulations show that the photoinduced excited states relax to a mixed state very fast, in which the lowest excited state is dominated.In the excited-state relaxation processes, the electron and hole are not separated. We have also studied the exciton dissociation by external electric field, and find that the critical electric field to dissociate the exciton is much lower than that calculated by previous Ehrenfest simulations in terms of low-level excited-state calculations.