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Title: Electrical and spectral characterisation of inkjet printed poly (3,4-ethylenedioxythiopene):poly(4-styrenesulphonate)
Author: Morris, David Jonathan
Awarding Body: University of Wales, Bangor
Current Institution: Bangor University
Date of Award: 2004
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This thesis describes a pioneering investigation in which time resolved scanning Kelvin probe microscopy (SKPM) and Raman spectroscopy were combined to identify processes occurring at the interface of inkjet printed poly(3,4- ethylenedioxythiophene): poly(4- styrenesulphonate) (PEDOT: PSS) and aluminium and indium tin oxide (ITO) electrodes. In order to undertake these measurements an experimental inkjet printing system was designed and constructed capable of robustly inkjetting polymer solutions with micron resolution suitable for inkjetting typical polymer device structures. The main findings of the SKPM work showed; (i) that there was good charge transfer between ITO and polymer as indicated by the lack of a significant potential drop at the interface, however this was not the case with the aluminium electrodes where large potential drops were seen at the interface and (ii) that ionic impurities in the polymer migrated under an applied electric field to the electrodes where they were not discharged, resulting in a collapse of the potential across the bulk of the polymer. These mechanisms were likely to be those responsible for the I oc t-" behaviour seen in potential step response measurements. This behaviour was confirmed by the Raman spectroscopy which showed changes in the spectra in the range 1200 to 1600cm-1 related to the structure of the conjugated polymer backbone and its doping levels. The observed charge transfer and ionic migration results have significant implications for polymer devices including the efficiency and degradation of PLEDs and FETs and the operating mechanism of polymer memory devices.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available