Recombination of polaron and exciton in conjugated polymers

Both polarons and excitons, which are composite particles with internal lattice structure, play an important role in the transport and light-emitting properties of conjugated polymers for the use in, e.g., polymer based light-emitting diodes (LEDs). The scattering and recombination processes between a triplet exciton and a polaron are investigated using a nonadiabatic evolution method based on an extended Su-Schrieffer-Heeger model including interchain interactions. The results show that an excited polaron state can be formed, besides a triplet exciton is converted into a singlet exciton by the polaron. Moreover, the yields of both the singlet exciton and the excited polaron states increase with increasing interchain coupling strength. The excited polaron is luminescent due to radiative decay as is the singlet exciton. Therefore, our results indicate that the quantum efficiency of polymer LEDs could be enhanced by polaron-exciton recombination.