Dynamic recombination of polaron pair with impurity in conjugated polymers

Abstract The dynamic collision of an on-chain same charged polaron pair with an off-chain counterion trapped in an impurity molecule, under the influence of an external electric field, has been investigated using a nonadiabatic evolution method. We demonstrate that the bipolaron, the exciton and the trion are the main products in such a reaction, and that the trion can be formed by both the direct recombination of a positive polaron pair with a counterion and the secondary recombination of the formed bipolaron with either a trapped polaron, a charged defect, or an impurity of the opposite sign, which is consistent with the experimental evidence qualitatively. Meanwhile, our results show that the strength of the applied electric field and the impurity potential play important roles in the polaron pair-impurity collision. These results are expected to be helpful to understand the electroluminescence and conductivity in conjugated polymers.