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Title: Enhancing the conductivity of PEDOT:PSS on bulk substrates
Author: Thompson, B. T. A. H.
ISNI:       0000 0004 7224 3677
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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PEDOT:PSS was investigated, using the dopants TWEEN 80 and MEK. The mixture was applied as a thin film on a PET substrate using three techniques, spincoating, dipcoating and spraycoating, with an aim to produce a bulk manufacturing conductive material. The dopants also improved the film forming of PEDOT:PSS. There was a problem with adhesion and durability of the film to the substrate. Several different materials were investigated to solve this problem. The adhesion problem was solved by adding a layer of methyl cellulose between the substrate and the PEDOT:PSS layers which acted as an adhesion promotor. One of the aims of this project was to determine a bulk manufacturing method which is viable for PEDOT:PSS. Three manufacturing techniques were investigated to see how this affected the film quality, film conductivity, thickness, orientation, and durability. Spincoating gave thinner films with a final thickness of 1- 2 µm and was more conductive than films manufactured using dipcoating or spraycoating. Spincoated films made using the dopants enhanced the bulk conductivity of the starting material by two orders of magnitude from 1494 Ωcm for the 100 % PEDOT:PSS dispersion used as a starting material, to 25 Ωcm for the doped 97.22 % PEDOT:PSS. The dipcoated and spraycoated samples were enhanced by three orders of magnitude, although, overall the spincoated samples were the most conductive. The enhanced 95 % to 98 % PEDOT:PSS dispersion with additives TWEEN 80 and MEK samples, remained more conductive than the starting material even after 62 weeks of storage under air. It was found that storage under air caused an increase in resistivity over the stored time period in doped PEDOT:PSS and 100% PEDOT:PSS films. High voltage studies up to 50V proved the material withstands repeated high voltage application over a period of 62 weeks. The mechanism of charge transport in the 97 % and 98 % PEDOT:PSS samples was found, using UV, to be due to the formation of polarons. Polaron charge carriers were formed when the polymer became ionised, lost an electron, and formed a positive charge on the polymer chain. In order to stabilise this the PEDOT molecule changes shape from the aromatic to the quinoid conformation. The most conductive films were found to be predominantly in the quinoid form whereas the less conductive films were mainly aromatic.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TP Chemical technology