Photocurrent kinetics of group III metal–(phthalocyaninato)–halogen complexes in vacuum and oxidising gas atmospheres

Abstract

The photoconductivity and photocurrent kinetics of the metal–(phthalocyaninato)chloro complexes, M(pc)Cl (M = Al, Ga or In), are reported in high vacuum (10^–6 Torr), oxygen and nitrogen dioxide. In vacuum it is shown that the photocurrent rise and decay kinetics of Al(pc)Cl are slow compared to those of the Ga(pc)Cl due to the disorder of the Al(pc)Cl molecule on its lattice site. The electrical properties of the M(pc)Cl complexes are compared to those of the homopolymeric [M(pc)F]_n(M = Al or Ga) complexes. The photocurrent rise times of [Ga(pc)F]_n in vacuum are longer than the corresponding rise times of Ga(pc)Cl, due to a difference in crystal quality. Nitrogen dioxide is shown to increase the conductivity and photoconductivity of the M(pc)X complexes. Oxygen has a similar, but smaller, effect on the M(pc)Cl (M = Al or In) and [M(pc)F]_n(M = Al or Ga) complexes. However, oxygen was found to decrease the conductivity of the Ga(pc)Cl complex. The photocurrent rise times of the complexes were found to be relatively unaffected by the presence of adsorbed species. The photocurrent decay times were, however, significantly increased by the presence of the gases; this is due to an increase in the number and depth of surface charge-carrier trapping sites.