We report numerical simulation results on hole transport in layers of the organic polymer poly(3-hexylthiophene) (P3HT) of different nanostructures based on a deterministic, phenomenological drift diffusion-reaction model that accounts for hole trapping-detrapping kinetics. The model is used to characterize the various P3HT layers examined in terms of their hole transport dispersivity. The model reproduces well experimental data of photocurrent evolution in P3HT samples ranging from drop cast thin films to surfactant-stabilized nanoparticle assemblies, explains the role of excess surfactant molecules in hole trapping for assemblies of P3HT nanoparticles, and demonstrates quantitatively the potential of using nanoparticle assemblies in organic photovoltaic devices. (C) 2014 Elsevier B.V. All rights reserved.