EFFECT OF IODINE INCORPORATION ON THE ELECTRICAL-CONDUCTIVITY OF FILMS OF NICKEL PHTHALOCYANINE

Films of phthalocyanine dyes are increasingly being utilized to photosensitize a variety of optoelectronic devices. One practical limitation to further application is the insulating nature of these films. In this paper, we demonstrate how permanently conductive (2 Ω-1 cm-1) films of NiPc films can be prepared by heating in an iodine ambient at temperatures ranging from 140 to 200 °C. (Pleating in iodine at lower temperatures results in NiPc films which were only transiently conductive.) These changes in conductivity are accompanied by changes in the optical absorption, morphology, and X-ray diffraction. Before treatment in iodine, the NiPc films are blue and have a sharp absorption edge at 750 nm. In contrast, the iodized NiPc films are green and have a less pronounced absorption edge at 700 nm with an additional absorption peak at 978 nm. The iodine treatment also resulted in some cracking in the NiPc film. Although the blue and green NiPc films are both tetragonal, there are pronounced shifts in the X-ray diffraction peaks, and the green films are preferentially oriented along the (200) direction. Copyright © 1979, American Chemical Society. All rights reserved.