Evidence of high charge mobility in photoirradiated polythiophene-fullerene composites

Interpenetrating networks of polythiophenes and fullerene derivatives give rise to charge transfer after irradiation with visible light. The resulting radical ion pairs have been studied by time-resolved EPR spectroscopy. At low temperatures (20 K), the radical pairs are spin correlated and locked at a distance of 27.1 A, whereas an increase of temperature causes the electron and the hole to move further away from each other.