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Mixing and Interfacial Composition in Polymer/Fullerene Thin Films / Elizabeth L. Hynes

DOI (Published version): 10.23889/Suthesis.51642

Abstract

Organic photovoltaic (OPV) devices use polymers and small-molecules, such as fullerenes,and offer an alternative to conventional inorganic devices. To achieve commercial success OPV devices require well-controlled morphologies and increased device lifetimes. The film morphology of these devices is c...

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Published: 2018
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa51642
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first_indexed 2019-09-02T14:49:54Z
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fullrecord <?xml version="1.0"?><rfc1807><datestamp>2019-09-03T11:45:01.3956505</datestamp><bib-version>v2</bib-version><id>51642</id><entry>2019-09-02</entry><title>Mixing and Interfacial Composition in Polymer/Fullerene Thin Films</title><swanseaauthors/><date>2019-09-02</date><abstract>Organic photovoltaic (OPV) devices use polymers and small-molecules, such as fullerenes,and offer an alternative to conventional inorganic devices. To achieve commercial success OPV devices require well-controlled morphologies and increased device lifetimes. The film morphology of these devices is complex: both mixing and crystallisation can occur. In this thesis, the fundamental behaviour of two model polymer/fullerene systems is investigated. The impact of parameters such as film thickness, molecular weight (MW) of the polymer and annealing temperature, on crystallisation and mixing are examined.The effect of MW on the mixing and interface width (between phases with different compositions) in fullerene/polymer systems is presented. These effects are examined in polymer/fullerene bilayers that are annealed at a range of temperatures close to or a few tens of degrees above the (bulk) glass transition temperatures of the materials. Neutron reflectivity is used to probe the composition profile within bilayer thin-films, and optical microscopy and atomic force microscopy (AFM) are used to observe crystal morphology. The fullerenes used are phenyl-C60-butyric acid methyl ester (PCBM) and bis-adduct phenyl-C60-butyric acid methyl ester (bis-PCBM). The polymer used is polystyrene (PS) which is chosen due to its low polydispersity and well-characterised behaviour in thin-films. Stable bilayer composition profiles are observed after annealing, and significant evidence is found for an MW dependence of the interfacial width. The observed behaviour supports the hypothesis that these systems represent a liquid-liquid equilibrium. The behaviour is also found to be broadly in agreement with theoretical predictions.Preliminary evidence is also presented regarding the impact of fullerene oxidation on mixing in these systems, which is observed to have a significant MW-dependence. Annealing at higher temperatures (well above the glass transition temperature of the materials) results in the growth of large (micron-sized) fullerene crystals in PCBM/PS bilayer samples. The observed morphologies of these crystals are found to be dependent on the PCBM layer thickness.</abstract><type>E-Thesis</type><journal/><publisher/><keywords>Polymer, fullerene, thin films, neutron reflectivity, scattering, organic photovoltaics, materials, characterisation, crystallisation, degradation, annealing, bilayers</keywords><publishedDay>31</publishedDay><publishedMonth>12</publishedMonth><publishedYear>2018</publishedYear><publishedDate>2018-12-31</publishedDate><doi>10.23889/Suthesis.51642</doi><url/><notes>All third party content is reproduced with permission of the copyright holder or under the terms of a Creative Commons licence.</notes><college>COLLEGE NANME</college><CollegeCode>COLLEGE CODE</CollegeCode><institution>Swansea University</institution><degreelevel>Doctoral</degreelevel><degreename>Ph.D</degreename><degreesponsorsfunders>Swansea University</degreesponsorsfunders><apcterm/><lastEdited>2019-09-03T11:45:01.3956505</lastEdited><Created>2019-09-02T10:53:40.8081595</Created><path><level id="1">Faculty of Science and Engineering</level><level id="2">School of Engineering and Applied Sciences - Uncategorised</level></path><authors><author><firstname>Elizabeth L.</firstname><surname>Hynes</surname><order>1</order></author></authors><documents><document><filename>0051642-02092019105806.pdf</filename><originalFilename>Hynes_Elizabeth_FINAL.pdf</originalFilename><uploaded>2019-09-02T10:58:06.5600000</uploaded><type>Output</type><contentLength>15992362</contentLength><contentType>application/pdf</contentType><version>E-Thesis &#x2013; open access</version><cronfaStatus>true</cronfaStatus><embargoDate>2020-07-01T00:00:00.0000000</embargoDate><copyrightCorrect>true</copyrightCorrect></document></documents><OutputDurs/></rfc1807>
spelling 2019-09-03T11:45:01.3956505 v2 51642 2019-09-02 Mixing and Interfacial Composition in Polymer/Fullerene Thin Films 2019-09-02 Organic photovoltaic (OPV) devices use polymers and small-molecules, such as fullerenes,and offer an alternative to conventional inorganic devices. To achieve commercial success OPV devices require well-controlled morphologies and increased device lifetimes. The film morphology of these devices is complex: both mixing and crystallisation can occur. In this thesis, the fundamental behaviour of two model polymer/fullerene systems is investigated. The impact of parameters such as film thickness, molecular weight (MW) of the polymer and annealing temperature, on crystallisation and mixing are examined.The effect of MW on the mixing and interface width (between phases with different compositions) in fullerene/polymer systems is presented. These effects are examined in polymer/fullerene bilayers that are annealed at a range of temperatures close to or a few tens of degrees above the (bulk) glass transition temperatures of the materials. Neutron reflectivity is used to probe the composition profile within bilayer thin-films, and optical microscopy and atomic force microscopy (AFM) are used to observe crystal morphology. The fullerenes used are phenyl-C60-butyric acid methyl ester (PCBM) and bis-adduct phenyl-C60-butyric acid methyl ester (bis-PCBM). The polymer used is polystyrene (PS) which is chosen due to its low polydispersity and well-characterised behaviour in thin-films. Stable bilayer composition profiles are observed after annealing, and significant evidence is found for an MW dependence of the interfacial width. The observed behaviour supports the hypothesis that these systems represent a liquid-liquid equilibrium. The behaviour is also found to be broadly in agreement with theoretical predictions.Preliminary evidence is also presented regarding the impact of fullerene oxidation on mixing in these systems, which is observed to have a significant MW-dependence. Annealing at higher temperatures (well above the glass transition temperature of the materials) results in the growth of large (micron-sized) fullerene crystals in PCBM/PS bilayer samples. The observed morphologies of these crystals are found to be dependent on the PCBM layer thickness. E-Thesis Polymer, fullerene, thin films, neutron reflectivity, scattering, organic photovoltaics, materials, characterisation, crystallisation, degradation, annealing, bilayers 31 12 2018 2018-12-31 10.23889/Suthesis.51642 All third party content is reproduced with permission of the copyright holder or under the terms of a Creative Commons licence. COLLEGE NANME COLLEGE CODE Swansea University Doctoral Ph.D Swansea University 2019-09-03T11:45:01.3956505 2019-09-02T10:53:40.8081595 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised Elizabeth L. Hynes 1 0051642-02092019105806.pdf Hynes_Elizabeth_FINAL.pdf 2019-09-02T10:58:06.5600000 Output 15992362 application/pdf E-Thesis – open access true 2020-07-01T00:00:00.0000000 true
title Mixing and Interfacial Composition in Polymer/Fullerene Thin Films
spellingShingle Mixing and Interfacial Composition in Polymer/Fullerene Thin Films
,
title_short Mixing and Interfacial Composition in Polymer/Fullerene Thin Films
title_full Mixing and Interfacial Composition in Polymer/Fullerene Thin Films
title_fullStr Mixing and Interfacial Composition in Polymer/Fullerene Thin Films
title_full_unstemmed Mixing and Interfacial Composition in Polymer/Fullerene Thin Films
title_sort Mixing and Interfacial Composition in Polymer/Fullerene Thin Films
author ,
author2 Elizabeth L. Hynes
format E-Thesis
publishDate 2018
institution Swansea University
doi_str_mv 10.23889/Suthesis.51642
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Uncategorised{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Uncategorised
document_store_str 1
active_str 0
description Organic photovoltaic (OPV) devices use polymers and small-molecules, such as fullerenes,and offer an alternative to conventional inorganic devices. To achieve commercial success OPV devices require well-controlled morphologies and increased device lifetimes. The film morphology of these devices is complex: both mixing and crystallisation can occur. In this thesis, the fundamental behaviour of two model polymer/fullerene systems is investigated. The impact of parameters such as film thickness, molecular weight (MW) of the polymer and annealing temperature, on crystallisation and mixing are examined.The effect of MW on the mixing and interface width (between phases with different compositions) in fullerene/polymer systems is presented. These effects are examined in polymer/fullerene bilayers that are annealed at a range of temperatures close to or a few tens of degrees above the (bulk) glass transition temperatures of the materials. Neutron reflectivity is used to probe the composition profile within bilayer thin-films, and optical microscopy and atomic force microscopy (AFM) are used to observe crystal morphology. The fullerenes used are phenyl-C60-butyric acid methyl ester (PCBM) and bis-adduct phenyl-C60-butyric acid methyl ester (bis-PCBM). The polymer used is polystyrene (PS) which is chosen due to its low polydispersity and well-characterised behaviour in thin-films. Stable bilayer composition profiles are observed after annealing, and significant evidence is found for an MW dependence of the interfacial width. The observed behaviour supports the hypothesis that these systems represent a liquid-liquid equilibrium. The behaviour is also found to be broadly in agreement with theoretical predictions.Preliminary evidence is also presented regarding the impact of fullerene oxidation on mixing in these systems, which is observed to have a significant MW-dependence. Annealing at higher temperatures (well above the glass transition temperature of the materials) results in the growth of large (micron-sized) fullerene crystals in PCBM/PS bilayer samples. The observed morphologies of these crystals are found to be dependent on the PCBM layer thickness.
published_date 2018-12-31T04:03:37Z
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score 11.013148

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