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Structural and Electrical Characterization of Discotic Liquid Crystalline Phthalocyanine for Application in Organic Devices

by Muriithi, Beatrice Wanjiku.

Abstract (Summary)
This thesis focuses on characterization of the structural and electrical properties of 2, 3, 9, 10, 16, 17, 23, 24-Octa (2-hydroccinamyloxyethylsulfanyl) copper phthalocyanine (hydrocinnamyl-Pc (5)) and the effect of solvent on these properties both in solution and in the thin films. Film coherence, microstructure (the spacing and orientation of adjacent molecules) and electrical properties (ohmic vs. rectifying contacts, diode quality) are all strongly dependent upon processing conditions. Recent advances in the design and organization of discotic liquid crystal materials for use in organic electronic devices have shown that the electronic properties of these materials depend on orientation, grain boundaries and defects in the thin films. We have studied this specific liquid crystalline phthalocyanine, modified with thioether-linked side chains, on modified substrates in several different solvent systems. In this work we looked at the effect of four solvents: chloroform, benzene, chlorobenzene and trichlorobenzene on molecular structure and thin film morphologies. We observed different aggregation properties both in solution and in the bulk, with benzene producing the largest aggregation effects and trichlorobenzene the least. The packing of this material was also found to depend on the solvent used for preparation of either the thin films or powders. In all cases, the molecules were tilted rather than in a cofacial orientation, also confirmed with FTIR, due to sulfur-sulfur interactions between adjacent Pc molecules. However, all the thin films prepared showed the typical columnar hexagonal packing of discotic materials, with trichorobenzene giving the highest columnar coherence and chloroform giving the least. 22 Pc (5) thin films form ohmic contact with gold electrodes and rectifying contacts with silver and aluminum contacts (ITO is used as the substrate). However, the electrical properties were found to be influenced by the morphology of the films, which depends on preparation conditions. 23
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School:The University of Arizona

School Location:USA - Arizona

Source Type:Master's Thesis

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