Hole transport in molecularly doped polymers (MDPs) is modelled as random walks in a bias field E over organic donors D embedded in a polymer matrix. Positional disorder for donor fraction p < 1 is represented by randomly placing donors at sites in a fcc lattice, while energetic disorder is given by a Gaussian distribution of site energies with width σ and spatial correlations in a sphere of radius Rc. Random walks generated by Marcus or small polaron rates for steps between nearby donors yield the mobility μ(E, T). In addition to σ and R_c, the rates depend on the parameters n and u for the distance dependence and reorganization energy respectively. With tritolylamine (TTA) in polystyrene as the paradigm, a procedure is presented for fixing the interdependent parameters σ, λ, γ and R_c that reproduce the field and temperature dependences of μ(E, T) over a wide range of p that includes dilute systems with different TTA packings enforced by saturated bonds. Positional disorder exceeds energetic disorder in dilute systems and yields constant μ(E, T_0) near room temperature. Joint modelling of TTA and related systems accounts for the characteristic μ(E, T) of MDPs and substantially extends the picture of hopping between localized states, with γ increased by about 15 and σ reduced by about 25 from conventional analysis using the Gaussian disorder model. Similar parameter changes are expected in other MDPs based on the compensation temperature T_0 and on scaling TTA results.
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