The Study On Effect Of Molecular Elasticity In Diblock Copolymers

Within an extended Su-Schrieffer-Heeger model including interchain interactions, the influence of molecular elasticity on the dynamics of photoexcitations and charge transport of polaron in one-dimensional (1D) diblock copolymers was studied by using a adiabatic evolution method. In organic-based light emitting devices, due to the difference in molecular elasticity between the two polymer segments, there exists a barrier for charge carrier tunneling. As electrons are injected into the copolymers, polarons will form due to the interaction between electrons and phonons. Then electric fields are applied along the polymer. If the electronic field strength is weak, the polaron can not tunnel the barrier and just move to the border of the two polymer segments. The polaron will tunnel the barrier and then move along the polymer chain at a critic field strength. The critic field strength can be effectively reduced by increasing the kinetic energy of the electron or increasing the length of the chains. However, by increasing the elasticity difference between the two polymer segments, the critic field strength is increased. There also exists response of valence band charge at bigger field strength.Free electron was excited to energy level of the conduction band near the Fermi surface successively, while the hole was retained at the top of valence band. A localized exciton in one single chain and a spread exciton between two chains are obtained.