Influence of ambient atmosphere on charge transport in polycrystalline thin films of three simple aromatic hydrocarbons.

Drift mobility of charge carriers in p-terphenyl, p-quaterphenyl and tetracene polycrystalline thin films was measured using the classical time-of-flight method. The measurements were carried out both in the atmosphere and in vacuum of the order of 10( - 3) Torr. The mobility measured in the atmosphere is of the order of 10(-4)cm2 V(-1) s(-1) and turns out to be about 1 order of magnitude higher than that measured in vacuum. It is suggested that the hopping transport of charge dominates in the structures investigated. The increase in the mobility for the measurements in the atmosphere probably results from the additional localized states due to water and other atmosphere molecules.