Interchain delocalization of an exciton in conjugated polymers

Optical excitations in conjugated polymers are considered primarily as intrachain one-dimensional excitons, while interchain coupling may be also important in the dynamical processes of excited states. Two aspects of interchain effects on excitons are discussed theoretically. The first one is the Frenkel-exciton type excitation transfer due to the Coulomb coupling. We examine how the excitation transfer rate depends on the chain length, the interchain distance, and the state. The other aspect is charge transfer due to the direct overlap of atomic orbitals. We demonstrate that the one-dimensional nature of the lowest exciton is not much altered by the interchain coupling. On the other hand, charge-transfer exciton states are located fairly close to the lowest intrachain exciton, so that they may be important in the dynamical processes of excited states, although they do not have large oscillator strength in the absorption spectrum.