Extrinsic photoconductivity in liquid aromatic hydrocarbons

Abstract

This paper is concerned with the criteria which have to be satisfied by an electrode + liquid aromatic hydrocarbon system, in order that photoconduction be observable. It is essential that the rate of electron exchange between an electronically excited molecule and the electrode be comparable with or greater than the rate of quenching of the excitation energy by the electrode. It is expected that this requirement is satisfied only by triplet excited molecules. Secondly, the energy level of the electrode most accessible to the excited molecule must be within a certain energy range with respect to the Fermi level. This criterion enables a classification of electrodes, according to work function, to be made for any particular liquid, into those electrodes which either oxidize or reduce, neither oxidize nor reduce, only oxidize or only reduce the excited molecules. Hence some conclusions are drawn about rectification in the system.