Abstract

Hole transport in molecularly doped polymers 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 † and spatial correlations in a sphere of radius R c . Random walks generated by Marcus or small polaron rates for steps between nearby donors yield the mobility w . In addition to † and R c , the rates depend on the parameters n and u for the distance dependence and reorganization energy respectively. With tritolylamine in polystyrene as the paradigm, a procedure is presented for fixing the interdependent parameters † , u , n and R c that reproduce the field and temperature dependences of w 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 w near room temperature. Joint modelling of TTA and related systems accounts for the characteristic w of MDPs and substantially extends the picture of hopping between localized states, with n increased by about 15% and † 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