CURRENT-VOLTAGE CHARACTERISTICS OF A PHTH ALOCYANINE FILM PREPARED BYTHE AQUEOUS COATING METHOD

Current-voltage characteristics of organic thin film cells were invest igated. epsilon-type copper phthalocyanine thin film (epsilon-CuPc) wa s deposited on an Al substrate by the aqueous coating method. The cell structure was Al/epsilon-CuPc/Mt (Mt=Pt, ITO (indium tin oxide), Au, SnO2 and Al). The dark current of the cells suggests the existence of an intermediate layer at Al plate/epsilon-CuPc interface. Auger electr on spectroscopic analysis of this layer revealed that it was an oxide layer with an O/Al ratio of 1.2 that grew simultaneously with electroc hemical deposition of epsilon-CuPc film. The dark current-voltage char acteristics also showed barrier formation at Al plate/oxide layer inte rface. Irradiation with white light through the Mt electrode indicated that photoactive region was at oxide layer/epsilon-CuPc interface and that the internal electric field was equal in direction to that forme d at Al plate/oxide layer. Plots of photovoltage and energy conversion efficiency (eta) vs, work function of Mt revealed that epsilon-CuPc f ormed ohmic contact with Au, ITO and Pt and showed that eta was larges t when the ionization potential of Mt was equal to that of epsilon-CuP c, 5.1 eV.