  In this work we use a three-dimensional Pauli master equation to investigate
the charge carrier mobility of a two-phase system, which can mimic
donor-acceptor and amorphous- crystalline bulk heterojunctions. Our approach
can be separated into two parts: the morphology generation and the charge
transport modeling in the generated blend. The morphology part is based on a
Monte Carlo simulation of binary mixtures (donor/acceptor). The second part is
carried out by numerically solving the steady-state Pauli master equation. By
taking the energetic disorder of each phase, their energy offset and domain
morphology into consideration, we show that the carrier mobility can have a
significant different behavior when compared to a one-phase system. When the
energy offset is non-zero, we show that the mobility electric field dependence
switches from negative to positive at a threshold field proportional to the
energy offset. Additionally, the influence of morphology, through the domain
size and the interfacial roughness parameters, on the transport was also
investigated.
