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 O2 or H2. Combination of scanning electron microscopy (SEM), infrared spectroscopy (ATR-FTIR), visible absorbance spectroscopies, and X-ray diffraction indicates that typical GaPc-Cl films consist of a mixture of at least two different phases, with different proportions of each depending upon growth conditions. High-temperature O2 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 O2 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.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry