The photoelectrochemlcal 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 (K^) 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 ( 6 Torr) vacuums, as opposed to the stoichiometric quantities of oxygen found in films deposited under ultrahigh vacuum.

No abstract

No abstract

Thin films of vacuum-deposited chlorogallium phthalocyanine (GaPc-Cl) and other trivalent-metal Pc's show widely variable photoelectrochemical properties depending upon vacuum deposition conditions and postdeposition doping with either 02 or H2. Combination of scanning electron microscopy (SEM), infrared spectroscopy (ATR-FTIR), visible absorbance spectroscopies, and X-ray diffraction indicates that typical GaPp-Cl films consist of a mixture of at least two different phases, with different proportions of each depending upon growth conditions. High-temperature 02 doping of GaPc-Cl can turn a film that behaves like a lightly doped semiconductor into a p-type material; H2 doping can reverse the effect. ESR experiments indicate the presence of high concentrations of radical species (ca. 1017 cm'3) whose populations can be increased or decreased with 02 or H2 doping, respectively. Photocurrent yield spectra of lightly doped or p-type GaPc-Cl films confirm that photocurrents are limited by hole transport in the first instance and electron transport in the second instant.

No abstract