Modulated photocurrent of evaporated copper phthalocyanine thin films

The photoelectrical behavior of evaporated copper phthalocyanine (CuPc) thin film sandwich-type and coplanar-type cell were investigated using a modulated photocurrent measurement technique. The modulated photocurrent sandwich-type cell showed a minimum value at the equilibrium point of photovoltage and applied voltage, and a phase shift of the modulated photocurrent showed a drastic change of 180 degrees in the vicinity of this point. As for the crystalline growth and decreasing the grain boundary, the amplitude of the modulated photocurrent increased with the increase of substrate temperature at deposition times. A varying point of the phase shift in the long wavelength region of the coplanar-type cell is considered corresponding to the energy band gap of the CuPc, of which value is determined to be 1.65 eV. (C) 1998 Elsevier Science S.A. All rights reserved.