Photoconductivity measurements in lead phthalocyanine thin films

Abstract

Lead phthalocyanine thin films (PbPc) were prepared by vacuum sublimation under a pressure of 10(-5) Torr. Photoconductive studies as a function of applied voltage, intensity of incident light, temperature and wavelength were carried out. Photocurrent spectra as a function of wavelength indicate peaks around 1.54, 1.98, 2.4, 3.0 and 3.48 eV. These are interpreted as transitions at critical points. From the temperature dependence of photoconductivity measurements, the activation energies 0.074 and 0.46 eV were obtained and 0.68 and 0.46 eV for dark conductivity. The dependence of the intensity of photocurrent yields a slope of m = 0.6, in the photoconductivity equation I-ph proportional to (In)(m). An energy level diagram is drawn for lead phthalocyanine thin films from the photoresponse studies. (C) 1999 .