The new method of sensitization of organic layers in electrophotography

Anthracene was the first photoconductor on which Carlson obtained electrophotographic images in 1938. Kallmann and his co-workers demonstrated that, using electrolytes as contacts for aromatic hydrocarbons, carrier injection into the crystal takes place. In the present paper, conditions for injection of electrons and holes into organic semiconductors from electrolytic contacts in which photochemical reactions are going on are analyzed. Specifically, anthracene and iodous hydrogen acid are examined. It has been shown that, using iodous hydrogen acid as a positive electrode, the photochemical reaction of decomposing molecular iodine into atoms leads to the injection of holes into anthracene. This phenomenon has been used to establish a new method of obtaining the latent electrophotographic image in anthracene. In these experiments, a solution of partly decomposed iodous hydrogen acid with various iodine contents was used as a substratum of the electrophotographic layer (anthracene). The surface of the layer was charged with the negative oxygen ions from the corona discharge in the air. The layer was exposed in the visible region (lambda=6500 A), where the photodissociation takes place. As this dissociation leads to the increasing density of the injection current from the electrolyte into the crystal, the illumination of the system in the visible region results in the fast discharge of the layer although the conductivity of the anthracene proper is insignificant in the visible region. Thus, the phenomenon of the photoactive electrolyte injecting holes into a crystal enables the formation of latent electrophotographic images in the visible part of the spectrum. In this paper, the kinetics of the discharge of the anthracene in the conditions of injection and the fulfillment of the reciprocity law have been investigated.