Abstract
Charge transfer processes and charge mobility are investigated in the poly(p-phenylenevinylene) model system. Realistic disordered polymer conformations are created and used in a coarse-grained model. Localized and quasiextended states are obtained using the Holstein Hamiltonian. Charge transport is modeled as an incoherent hopping mechanism in the framework of unimolecular and bimolecular Marcus theory for intramolecular and intermolecular processes, respectively, to account for the electron-phonon coupling present in π-conjugated polymer systems. Static and quasidynamic disorder effects are both considered using the “fluctuating bridges” approach. Charge mobility is calculated using kinetic Monte Carlo simulations for a range of physically relevant parameters. We examine the relative importance of intramolecular and intermolecular mechanisms and the role of localized and extended states in the transport process. We discuss the role of disorder and temperature and show that a log μ∝−F electric field dependence in the high field regime naturally emerges from our model. We show that disorder significantly reduces the mobility at low fields but slightly increases it at high fields. We also show that the mobility is dominated by interchain charge transfer between low energy localized states at low fields, but at higher fields, intrachain transfer to more delocalized higher energy states becomes equally important. This crossover is the cause of anisotropic charge mobility at intermediate field strengths.
Published Version
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