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The recombination dynamics of singlet and triplet oppositely charged polarons under the influence of electron–electron (e–e) interactions in coupled polymer chains are investigated using a multi-configurational time-dependent Hartree–Fock (MCTDHF) method. During recombination processes, singlet and triplet intrachain excitons are important products. By calculating the yields of the singlet and triplet intrachain excitons as a function of the on-site and long-range e–e interactions, it is found that the yields of the singlet and triplet intrachain excitons both decrease with increasing on-site e–e interactions. On the other hand, as the long-range e–e interactions increase, the yields of singlet intrachain excitons initially increase and then maintain a constant value, while the yields of the triplet intrachain excitons decrease. Our results show that the long-range e–e interaction is of fundamental importance and improves the luminescence efficiency in coupled polymer chains. Finally, the influence of the polymer chain length on the yields of singlet and triplet intrachain excitons is discussed. [ABSTRACT FROM AUTHOR]

The formation and evolution of photogenerated soliton pairs in trans -polyacetylene is simulated by using a nonadiabatic dynamical method. Electron–lattice interaction as well as electron correlation effects are both included by employing the Su–Schrieffer–Heeger+Pariser–Parr–Pople model. We adopt the multiconfigurational time-dependent Hartree–Fock formulas which allows for the distinguishing between charged and neutral soliton pairs. It is found that charged soliton pairs are created in the initial stage of the evolution after photoexcitation. Subsequently, the formed charged soliton pairs transform into neutral ones during the dynamical evolutions. The conversion time from charged to neutral state depends on the strength of Coulomb interactions. However, neutral soliton pairs are suppressed in the non-interacting limit, which is in good agreement with the previous estimates based on the Su–Schrieffer–Heeger model. We hope these results can provide further insight into some of the basic issues of interest in photogenerated processes in conducting polymers. • We have studied the formation and evolution of photogenerated soliton pairs • Charged soliton pairs are created in the initial stage after the photoexcitation. • Charged pairs transform into neutral ones if e–e correlations are considered. • Neutral pairs are suppressed in the non-interacting limit. • e–e interactions are the key ingredient in driving the formation of neutral pairs. [ABSTRACT FROM AUTHOR]

Combining the Su–Schrieffer–Heeger and Pariser–Parr–Pople model (SSH+PPP), we have studied the influence of electron–electron interactions on the motion and dissociation of a polaron in the presence of an electric field, with emphasis on the long-range Coulomb interactions. The multiconfigurational time-dependent Hartree–Fock (MCTDHF) formalism was used to compute the electron–electron interactions. How the saturated velocity and the critical dissociation electric field of the polaron are related to the on-site Coulomb repulsion and long-range Coulomb interactions has been investigated. It was found that the on-site Coulomb interaction does not favor the motion of a polaron. There is a critical strength of the long-range Coulomb interaction for which the polaron takes on the most localized configuration. Comparing with the results obtained using the extended Hubbard model, we found that competition between the long-range Coulomb interactions and the on-site Coulomb interaction leads to a non-monotonic dependence of both the saturated velocity and the critical dissociation electric field on the long-range Coulomb interactions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]