Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.740991
Title: Roll-to-roll deposition of highly flexible organic-inorganic barrier layers for printed electronics and photovoltaics
Author: Tobin, Vincent
ISNI:       0000 0004 7230 5268
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2018
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Abstract:
This thesis investigates how to improve transparent flexible water vapour barriers by understanding how water permeates through them. The barriers consisted of a reactively sputtered aluminium oxide coating on an industrial-grade polypropylene substrate. Some also incorporated a di-acrylate smoothing layer. Key deposition conditions were studied and optimised for permeation and visible-light transparency: sputtering power, thickness & sequential deposition rate. One of the main deposition conditions corresponded to increasing coating nitrogen content in order to induce barrier-water interaction. The final investigation consisted of including acrylate layers in different barrier stacking combinations. It was found that thin, high sputter power coatings formed the best barriers to permeation. This was due to denser packing of the oxide and the inclusion of fewer macro-defects (large defects allowing unhindered permeation) and nano-defects (defects small enough to cause the permeant to interact with the coating). No clear benefit to permeation was found from the inclusion of nitrogen, but refractive index was seen to increase and the oxynitride coatings mechanically failed at a greater force than the oxides. This case illustrated the importance of considering the role of permeation through nano-defects: although a high activation energy was achieved for the nitrogen containing films, possibly suggesting greater interaction between the water vapour and the barrier, the amount of permeation was not reduced as the nitrogen gave rise to increased permeation due to nano-defects, thus changing the processing and chemistry can affect both the macro-defect and nano-defect permeation. Smoothing layers were found to reduce the permeation rate by covering large substrate features, thus allowing rough substrates to be used even for high barriers. Although a coating of acrylate on top of a barrier oxide showed no improvement, a 1-2-1-2 stack of smoothing layer (1) and oxide (2) was found to exhibit a large delay in the onset of permeation.
Supervisor: Assender, Hazel Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.740991  DOI: Not available
Keywords: Water permeation ; Gas Barrier
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