  We probe charge photogeneration and subsequent recombination dynamics in neat
regioregular poly(3-hexylthiophene) films over six decades in time by means of
time-resolved photoluminescence spectroscopy. Exciton dissociation at 10K
occurs extrinsically at interfaces between molecularly ordered and disordered
domains. Polaron pairs thus produced recombine by tunnelling with distributed
rates governed by the distribution of electron-hole radii. Quantum-chemical
calculations suggest that hot-exciton dissociation at such interfaces results
from a high charge-transfer character.
