Photoconduction in Aromatic Hydrocarbons

Photoconduction has been observed in single crystals of benzene, naphthalene, biphenyl and pyrene using the pulse technique. Experimental procedures have been found for the purification and crystal growth of the materials that produce specimens whose charge carrier lifetimes are sufficiently long to allow the measurement of drift mobilities, and thus to determine the number of charge carriers produced per pulse. A single-photon generation mechanism was observed only in pyrene. The other materials exhibited a photogeneration mechanism that depended quadratically on light intensity and was determined to be exciton-exciton collision ionization.