Dynamics study of the recombination of polaron pairs in polymer chain with impurities

Within a Su–Schrieffer–Heeger model modified to include an external electric field, the dynamical process of oppositely charged polarons in a polymer chain is simulated by using a non-adiabatic evolution method. It is found that the polaron pair can combine with neutral exciton in the presence of a weak electric field, and the field requirement for achieving exciton is very strict in a pure polymer chain. But under the assistance of impurities, the exciton can be produced under a wide range of applied field strengths. The yield of neutral exciton can reach as high as 96%, which is significant for electroluminescent efficiency of OLEDs.