Dynamical Mechanism of Polarons and Bipolarons in Poly(p-Phenylene Vinylene)

Studies on Poly(p-Phenylene Vinylene) (PPV) and derivatives have experienced enormous growth since they were successfully used to fabricate the first efficient prototypes of Polymer Light-Emitting Diodes in the 90s. Despite this rapid progress, understanding the relationship between charge transport and the morphology in these materials remains a challenge. Here, we shed light on the understanding of the transport mechanism of polarons and bipolarons in PPVs by developing a two-dimensional tight-binding approach that includes lattice relaxation effects. Remarkably, the results show that the PPV lattice loses the energy related to its conjugation during time by transferring this amount of energy to electrons. Such a process for energy transfer permits the quasiparticles to overcome the potential barrier imposed by the local lattice deformations, that are formed in the presence of an additional charge and, consequently, their electric field assisted transport takes place. Within the framework of this transport mechanism, a better insight into the origin of the carrier mobility in PPV and derivatives can be achieved and would be a useful guide for improving their chemical structures and morphologies.