Browsing by Subject "PEDOT"
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Item Layer-by-layer assembly of poly(3,4-ethylenedioxythiophene) thin films: tailoring growth and UV-protection(2009-05-15) Dawidczyk, Thomas JamesConductive thin films of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT-PSS) were created via layer-by-layer assembly. The PEDOT-PSS was used in an aqueous solution as an anionic polyelectrolyte, with both linear and branched polyethylenimine (PEI) and poly(allylamine hydrochloride) (PAH) in the positive aqueous solution. The electrical conductivity was varied by altering pH, concentration, polyelectrolyte, and doping the PEDOT with dimethylsulfoxide (DMSO). The most conductive 12BL samples were doped with 1wt% DMSO and have a sheet resistance of approximately 8k?/?. Despite exhibiting good initial conductivity, these PEDOT based thin films degrade under ultraviolet (UV) exposure. UV absorbing nanoparticles were added into the cationic solution in an effort to reduce UV sensitivity. The final bilayers of the films contained either colloidal titanium dioxide (TiO2) or carbon black (CB) and the films were exposed to a 365nm UV-light with an intensity of 2.16mW/cm2 for 9 days. The UV light at this intensity correlates to approximately four years of sunlight. The initial sheet resistances for all samples were similar, but the UV-degradation was reduced by a factor of 5 by utilizing TiO2 and CB in the final bilayers. In addition to being the most conductive after UV exposure, the TiO2 containing film was also 27% more optically transparent than the pure PEDOT films. These additional UV-absorbing nanoparticles extend the operational life of the PEDOT films and, in the case of TiO2, do so without any reduced transparency.Item Synthesis and Characterization of Polymer Composites Containing Aligned Conducting Polymers and Carbon Nanotubes(2014-04-21) Manda, SwathiMiniaturization of electronics and impending demand for bendable electronic gadgets creates a dire need for a thin and flexible film technology that would not only provide spot cooling for the crammed transistors, but also tap into the waste heat generated to produce a portable power source. Thin film thermoelectrics offer a viable solution and have several structural, chemical and economical advantages over inorganic thermoelectric materials. However, their low power factor compared to that of inorganic materials prevents them from being used for practical applications. The tradeoff between Seebeck coefficient and electrical conductivity restricts the improvement of power factor through increase in number of charge carriers. However, controlled modulation of the mobility of charge carriers has a potential to increase the electrical conductivity without adversely affecting the Seebeck coefficient. This research involves investigating a novel way to fabricate organic thermoelectric thin films with high power factor by modulating the morphology of the conducting polymer poly-(3,4-ethylenedioxythiophene) (PEDOT) and creating a composite with carbon nanotubes to control the mobility and hence the electrical conductivity of the thin films. Aligned PEDOT-carbon nanotube composite thin films were fabricated and characterized to study both the alignment of the polymer chains and change in their electrical conductivity. This research utilized the bottom up self organized molecular system templates to control the nano structure and ordering of the polymer?carbon nanotube composite. Liquid crystal template was used to capture all the monomer (3,4-ethylenedioxythiophene) EDOT molecules within the cylindrical cores of hexagonal mesophase oriented in effective net direction within domains, and the monomers were electro-polymerized to obtain aligned polymer chains. This aligned structure renders better anisotropic electrical conductivity along the polymer chain direction. A non percolated dispersion of carbon nanotubes and dopants was incorporated into the aligned PEDOT thin film by spraying as well as internally dispersing within the liquid crystal network before polymerization. The carbon nanotube and dopant incorporation into the aligned PEDOT thin films increased the electrical conductivity by about two orders of magnitude.