Photoconductor Fatigue. 2. Effect of Long-Wavelength Light on the Electrical and Spectroscopic Properties of Organic Layered Photoconductors

Electrical fatigue as a result of exposure to light emitted from lamps used to discharge photoconductors is a problem that limits the longevity of commercial organic photoconductors. We present data herein on a model organic layered photoconductor showing that the light initiates a solid-state photochemical reaction that is diffusion controlled and depends on the polymers used in the charge-transport layer. Most importantly, the reaction occurs at the interface of the charge generation and charge transport layers, between the hole-transport molecule p-(diethylamino)benzaldehyde diphenylhydrazone (DEH) and the carrier generation dye chlorodiane blue. The resultant photochemistry renders the organic photoconductor useless with regard to electrical properties. Depending upon the polymer chosen for the hole-transport layer, evolution of residual voltage during light decay, or an electrically conductive photoconductor in the dark, arises. Acidity in the hole-transport layer also appears to degrade the dark electrical properties upon exposure to discharge lamps. © 1991, American Chemical Society. All rights reserved.