Semiconducting properties of some μ-bridged phthalocyanines
The application of organic materials in electronic devices depends, in part, on the ability to control the electrical properties by structural modification. This thesis explores the possibility of modifyng the properties in the cofacially stacked polymeric phthalocyanine, fluoroaluminium phthalocyanine (AIPcF) by copolymerisation with the structurally related fluorogallium phthalocyanine (GaPcF). Copolymers of AIPcF and GaPcF of composition 2:1,1:1 and 1:2 were prepared for the first time. The purification, chracterisation, and evaluation of the 1:1 copolymer were carried out. It was found that the material could be purified by entrainer sublimation without major change in the composition. The polymeric nature of the material was established through spectroscopic methods, thermogravimetric analysis and X-ray powder diffraction. Evaluation of evaporated copolymer films by XPS, depth profiling by argon ion bombardment, and electron bombardment largely confirmed the expected composition but indicated that a limited amount of fractionation or selective decomposition had occurred. A detailed study of the properties of compactions and films by a.c. and d.c. show that the copolymer is intermediate between the monomers in its properties, and different from the mixture of the monomers. The a.c. measurements suggest that the films of both pure materials and copolymer have a higher imperfection concentration than the compaction. Two preliminary studies are also reported. Iodine doping of the copolymer leads to high conductivity which is limited by disorder. The photoconduction response of the copolymer is higher than that of either component, suggesting copolymerisation as a means of enhancing this property. The successful synthesis of this copolymer offers a route to the copolymerisation of electrically dissimilar materials as a means of enhancing the conductivity in linear chains.