We have studied the intermolecular carrier transport in ${\mathrm{C}}_{60}$ films. Photoelectrical and optical experiments indicate charge transfer transitions to set in at photon energies of ∼2.2 eV. The electron transport in the charge transfer state is by hopping with typical drift mobilities of 1 ${\mathrm{cm}}^2$/V s in as-grown films. Hole drift mobilities are in the ${10}^{-4}{\mathrm{cm}}^2/\mathrm{V}\mathrm{}\mathrm{s}$ range. Upon oxygen exposure the carrier mobilities decrease significantly, while recombination lifetimes grow. These findings are interpreted as being due to transport-limited recombination kinetics.

• Received 11 August 1998

DOI:https://doi.org/10.1103/PhysRevB.60.11804