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Thesis Paul Cowper 2016.Pdf University of Bath PHD Azulene-based Dyes for Dye Sensitised Solar Cells Cowper, Paul Award date: 2017 Awarding institution: University of Bath Link to publication Alternative formats If you require this document in an alternative format, please contact: [email protected] General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 04. Oct. 2021 Azulene-based Dyes for Dye Sensitised Solar Cells Paul Cowper A thesis submitted for the degree of Doctor of Philosophy University of Bath Department of Chemistry June 2017 COPYRIGHT Attention is drawn to the fact that copyright of this thesis rests with the author and copyright of any previously published materials included may rest with third parties. A copy of this thesis has been supplied on condition that anyone who consults it understands that they must not copy it or use material from it except as permitted by law or with the consent of the author or other copyright owners, as applicable. This thesis may be made available for consultation within the University Library and may be photocopied or lent to other libraries for the purposes of consultation. ............................................................................................................................ (date) ............................................................................................................................ (signature ) Science is the belief in the ignorance of experts. RICHARD P. FEYNMAN ii Contents 1 Introduction .......................................................................................................................1 1.1 Renewable Energy .....................................................................................................1 1.2 Energy from the Sun ..................................................................................................2 1.3 Photovoltaics .............................................................................................................2 1.3.1 Insulators and Conductors .................................................................................3 1.3.2 Semiconductors .................................................................................................4 1.3.3 Photovoltaic Cells ...............................................................................................4 1.3.4 Silicon p-n Junction ............................................................................................5 1.3.5 Silicon PV Cells – 1st Generation ........................................................................7 1.3.6 Thin Film PV Cells - 2nd Generation ....................................................................8 1.3.7 Dye Sensitised Solar Cells (DSSC) – Generation 2½? .........................................8 1.3.8 Dye Sensitisation of Semiconductors .............................................................. 10 1.4 Ru(II)-free Dyes for Dye Sensitised Solar Cells (DSSC) ............................................ 13 1.4.1 Introduction .................................................................................................... 13 1.4.2 Porphyrins and Chlorophyll Derivatives ......................................................... 14 1.4.3 Phthalocyanines .............................................................................................. 16 1.4.4 Coumarins, Indolines, Perylenes and Squarines ............................................. 17 1.4.5 Donor-[π Linker]-Acceptor (D-π-A) Dyes ........................................................ 19 1.4.6 Azulene Dyes ................................................................................................... 20 1.5 Azulene ................................................................................................................... 21 1.5.1 Electronic Structure and Colour ...................................................................... 22 1.5.2 Substituent Effects .......................................................................................... 25 1.5.3 Reactivity ......................................................................................................... 27 1.5.4 Common Reactions ......................................................................................... 28 1.5.5 Azulene Synthesis ........................................................................................... 32 2 Theory ............................................................................................................................. 43 2.1 Calculating DSSC Efficiency ..................................................................................... 43 2.2 Cyclic Voltammetry (CV) ......................................................................................... 46 2.3 UV/Vis Spectroscopy ............................................................................................... 52 3 Dye Design ...................................................................................................................... 59 3.1 Introduction ............................................................................................................ 59 3.2 Anchor Group .......................................................................................................... 59 3.3 Linker Group ........................................................................................................... 61 3.4 Molecular Orbital Models ....................................................................................... 62 3.5 Excited States .......................................................................................................... 66 iii 4 Azulene Dyes – 1st Generation......................................................................................... 69 4.1 Dye Az-1-tcaa (84) Proposed Synthetic Routes ....................................................... 69 4.1.1 Cyanoacrylic Acid Anchor Group ..................................................................... 69 4.1.2 Aldehyde Intermediate (87) ............................................................................ 69 4.2 Dye Synthesis Discussion ......................................................................................... 78 4.2.1 4,6,8-Trimethylazulene .................................................................................... 78 4.2.2 In-Situ Thiophene Ring Synthesis .................................................................... 78 4.2.3 Metalated Azulene Compounds for Cross Coupling Reactions ....................... 81 4.2.4 Azulenyl-1-triflate Synthesis ............................................................................ 83 4.2.5 Suzuki-Miyaura Cross-Coupling of 1-Chloroazulene with Boron Functionalised 2-Thiophenecarboxaldehyde ........................................................................................... 84 4.2.6 Azulene Dyes without Thiophene Linker ......................................................... 95 4.3 Dye Characterisation ............................................................................................... 96 4.3.1 NMR Spectroscopy .......................................................................................... 96 4.3.2 UV-Vis Spectroscopy ...................................................................................... 100 4.3.3 Infra-Red Spectroscopy ................................................................................. 104 4.3.4 Electrochemistry ............................................................................................ 104 4.3.5 Crystallography .............................................................................................. 108 4.3.6 Dye Sensitised Solar Cells .............................................................................. 109 4.4 Conclusions ............................................................................................................ 111 5 Azulene Dyes – 2nd Generation ...................................................................................... 113 5.1 Introduction ........................................................................................................... 113 5.2 Literature Compounds ........................................................................................... 115 5.2.1 1,3-Di-tert-butylazulene (160) ....................................................................... 115 5.2.2 1,3-Bis(methylthio)azulene (170) .................................................................. 116 5.2.3 N-tert -Butyl-alpha-(7-isopropyl-4-methyl-3-ethoxycarbonyl-azulen-1- yl)nitrone (175) .............................................................................................................. 118 5.2.4 Conclusions ...................................................................................................
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