Dynamics of exciton transfer in coupled polymer chains

Abstract

The dynamics of singlet and triplet exciton transfer in coupled polymer chains are investigated within the Su-Schrieffer-Heeger+Pariser-Parr-Pople model including both electron-phonon (e-p) coupling and electron-electron (e-e) interactions, using a multi-configurational time-dependent Hartree-Fock dynamic method. In order to explain the processes involved, the effects of on-site and long-range e-e interactions on the locality of the singlet and triplet excitons are first investigated on an isolated chain. It is found that the locality of the singlet exciton decreases, while the locality of the triplet exciton increases with an increase in the on-site e-e interactions. On the other hand, an increase in the long-range e-e interaction results in a more localized singlet exciton and triplet exciton. In coupled polymer chains, we then quantitatively show the yields of singlet and triplet exciton transfer products under the same interchain coupling. It is found that the yield of singlet interchain excitons is much higher than that of triplet interchain excitons, that is to say, singlet exciton transfer is significantly easier than that for triplet excitons. This results from the fact that the singlet exciton is more delocalized than the triplet exciton. In addition, hopping of electrons with opposite spins between the coupled chains can facilitate the transfer of singlet excitons. The results are of great significance for understanding the photoelectric conversion process and developing high-power organic optoelectronic applications.

Dynamics of charge separation at an organic donor-acceptor interface

“…The system can, however, be considered as a model system which is able to grasp the essentials of most (nondegenerate) conjugated polymers. We adopt the parameters developed by Miranda et al [19,20], which also were used in our previous work [18,21,22]. Specific attention is given to three parameters: the interchain hopping t v and t DA , the screening of the Coulomb potential β, and the band offset E. Three sets of simulations are presented below; in each such simulation we vary one of these parameters and keep the other two at a fixed value.…”

Exciton intrachain transport induced by interchain packing configurations in conjugated polymers

“…The result is consistent with the earlier static picture and the predictions. 33 In order to give an explanation to the above transport dynamical process, we then calculate the dependence of the exciton creation energy E with respect to the distance d between the two linearly coupled chains, as shown in Fig. 3.…”

“…As stated above, an exciton is always inclined to be localized in a region with a lower creation energy or stronger interchain coupling. 21,33 Here, we initially set the exciton to be photogenerated near the 20 th site of chain 1, which corresponds to a high-energy position for the exciton formation. Due to the energetic instability, the exciton will experience a relaxation and transport to the position with a low creation energy, during which the excess energy is dissipated with the form of lattice vibration by employing a dissipation term l in the model.…”

Concentration effects on intrachain polaron recombination in conjugated polymers

“…In order to better consider interaction between the quasi-particles we included electron-electron correlation through the extended Hubbard formalism with U = 1.0 eV and V = U/3, in accordance with values recently used in the literature. [33][34][35][36][37][38][39] We begin our discussion by presenting schematic diagrams of the energy levels for the different initial configurations considered in our work. In Fig.…”