Exciton formation with interchain couplings in organic polymers

Based on the framework of the tight binding approach and the nonadiabatic dynamics, the formation of an exciton in inter-coupled polymer chains is studied. Both a localized exciton in one single chain and a spread exciton between chains are obtained. It is found that an excited electron-hole pair is more inclined to evolve into a localized exciton, and the long range Coulomb e-e interaction is favorable to the exciton formation. By calculating the formation time of an exciton, we show that the optical response time is faster in a dilute solution than that in a solid film of polymer molecules.