Electrical Properties of Junctions Between Aluminuim and Poly[3-(2'-Octyloxy-5'-(1'''-Oxooctyl)Phenyl)Thiophene
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Date
2003-06
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Addis Ababa University
Abstract
In this thesis, the property of the junction between aluminium and neutral conjugated polymer
is studied. The conjugated polymer used is poly[3-(2'-octyloxy-5'-(1'''-
oxooctyl)phenyl)thiophene] which is the derivative of polythiophene having 8-carbon atoms
alkyl side chain which makes it different from other thiophene derivatives.
The techniques employed are optical absorption spectrum, I-V characterization and impedance
spectroscopy study. Optical spectroscopy study showed the optical band gap of the polymer is
2.03eV indicating the polymer is in the range of conventional inorganic semiconductor. Based
on this result the theoretical background in studying the property of junction between
aluminium and the polymer is that of conventional inorganic semiconductors.
The I-V characteristics of Al/poly[3-(2'-octyloxy-5'-(1'''-oxooctyl)phenyl)thiophene]/ITO
structure showed non-ohmic, non-rectifying and nearly symmetrical curves. The complex
impedance analysis exhibited a semicircle whose diameter depends on the magnitude of the
applied bias voltage; the diameters are small for larger bias voltages and increases for small
intermediate bias voltages. This result is consistent with the I-V characteristics. Therefore, the
junction between aluminum and the polymer forms no Schottky barrier
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Keywords
Electrical Properties of Junctions