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Solvent Vapor Imprinting of micro and nano-structures on polymeric thin films
Umeå University, Faculty of Science and Technology, Department of Physics.
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
Abstract [en]

The emerging organic photovoltaics (OPV) technology is based on the use of organic semiconducting materials, the conjugated polymers. Such materials allow thin film solar cells to be realized, representing a promising low-cost alternative to the traditional inorganic PV devices. However, their low power conversion efficiencies still limit their competitiveness on the energy market. In order to improve their performances, two main pathways can be followed: enhancing the electrical properties of polymers by improving their semicrystalline structure; or, developing new cell designs and geometries to increase the generated photocurrent. Film annealing processes and nano structures are very effective techniques for both the strategies, respectively. By solvent imprinting lithography(SIL) it is possible to create polymeric films characterized from the positive effects of both nanopatterned structures and solvent-vapour annealing. This thesis is the result of the research carried out by the author at the "Organic Electronicsand Biomimetics Laboratory" group of Umeå University within the project aimed to study and realize structured P3HT polymeric thin films imprinted by SIL. In particular, a lab-made SIL system was developed and tuned. The SIL procedure has been optimized checking samples quality by optical microscopy and atomic force microscopy (AFM): as a result, well-imprinted, high-quality microstructured patterns were successfully realized, stimulating further studies going down to the nanoscale. In addition, the inner semicrystalline structure of P3HT imprinted films has been analysed by X-ray diffraction(XRD): the crystallinity dependence on film thickness, film geometrical structure and solvent vapour annealing time has been studied. The results obtained in this work reveal that the polymer confinement in nano-dimensional spaces strongly influences both number and orientation of crystalline domains. Moreover, different crystalline grades can be realized by modulating the annealing time from 0 to 60 minutes, demonstrating the significative influence of the solvent vapour on the polymer structure: particularly, an optimal annealing time around 30 min. results to maximise the overall film crystallinity.

Place, publisher, year, edition, pages
2014.
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:umu:diva-106673OAI: oai:DiVA.org:umu-106673DiVA: diva2:843876
Subject / course
Fysik - examensarbete III
Educational program
Master's Programme in Physics
Available from: 2015-10-29 Created: 2015-07-31 Last updated: 2015-10-29Bibliographically approved

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