  Understanding the transport mechanism of electronic excitations in conjugated
polymers is key to advancing organic optoelectronic applications, such as solar
cells, OLEDs and flexible electronics. While crystalline polymers can be
studied using solid-state techniques based on lattice periodicity, the
characterisation of amorphous polymers is hindered by an intermediate regime of
disorder and the associated lack of symmetries. To overcome these hurdles we
use a reduced state quantum master equation approach based on the Merrifield
exciton formalism. Using this model we study exciton transport in conjugated
polymers and its dependence on morphology and temperature. Exciton dynamics
consists of a thermalisation process, whose features depend on the relative
strength of thermal energy, electronic couplings and disorder, resulting in
remarkably different transport regimes. By applying this method to
representative systems based on poly(p-phenylene vinylene) (PPV) we obtain
insight into the role of temperature and disorder on localisation, charge
separation, non-equilibrium dynamics, and experimental accessibility of thermal
equilibrium states of excitons in amorphous polymers.
