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Title: Thin film vapour barrier systems on vacuum-planarized polyester films
Author: Suttle, Helene
ISNI:       0000 0004 2721 4340
Awarding Body: Oxford University
Current Institution: University of Oxford
Date of Award: 2010
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The work contained in this thesis examines how the properties of gas barrier materials may be affected by the choice of deposition technique, substrate material, and surface treatment. The performance of barriers with respect to the requirements for the optoelectronics industry was studied, along with an appraisal of the metrics used to assess barrier levels. Polyester films were coated with aluminium oxide by reactive sputter deposition in an industrial-scale research web coater. The transparency and stoichiometry of coatings was achieved by control of the reactive gas supply levels, and the deposition configuration in the web coater. Target poisoning, which leads to low deposition rates, was controlled by balancing the inert and reactive gases and by changing the reactive gas supply locations. Barrier properties of the films were found to be affected strongly by the choice of power supply. By using a method of depositing many thin layers of AIOx sequentially to build up a single layer, it was possible to extend the region of high barrier performance out to thick coatings of several hundred nanometres and thus create very high barrier materials. PEN (polyethylene naphtha late) film was used as a substrate material for all samples. It is a good candidate for use as a substrate for barrier films due to its excellent thermal, mechanical, and barrier properties. The use of surface treatments to minimise the effect of substrate surface features was examined. It was found that for coating thicknesses greater than 50 nm the surface smoothing layers did not improve barrier properties, and coated films with no smoothing layer performed better in water vapour transmission tests. Fragmentation tests showed that the barrier performance of films was greatly affected by the adhesion between the substrate and aluminium oxide coating. Various methods for measuring barrier film properties were studied in this work. The standard steady-state test for gas transmission rates was compared with the non-standardised calcium test. Organic photovoltaic (OPV) devices were encapsulated with barrier films to measure to what extent they act as a barrier to contaminants such as water vapour and oxygen. In a separate experiment, a component material of the OPV devices, poly(3-hexylthiophene) (P3HT), was used successfully in encapsulation tests where its degradation was measured using UV-vis-nIR spectrometry.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available