The photoelectrochemical properties of vacuum-deposited thin films of titanyl phthalocyanine (TiOPc) are described. Continuous films between 60 and 400 nm in thickness show behavior like that of a highly doped p-type semiconductor, with open-circuit photopotentials (Voc) that vary linearly in magnitude with the formal potential of the contacting redox couple (up to 0.7 V). Comparison of photocurrent action spectra and transmission absorbance spectra showed that two distinct phases of TiOPc were deposited from vacuum, having different absorbance maxima at ca. 720 and 820 nm. The TiOPc phase with the more red-shifted absorbance appeared to possess higher photoactivity. X-ray photoelectron spectroscopy (XPS) of both TiOPc and vanadyl phthalocyanine films (VOPc) showed clearly the presence of extra oxygen forms for films vacuum deposited in moderate (10-6 Torr) vacuums, as opposed to the stoichiometric quantities of oxygen found in films deposited under ultrahigh vacuum.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry