Thesis
Electronic evaluation of organic semiconductors towards electronic devices
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2013
- Thesis identifier
- T13526
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Organic π-conjugated macromolecules, (polymers and oligomers) are an important class of semiconductor which are used in applications such as: field effect transistors, photovoltaics, organic light emitting diodes and electrochromic devices. The π-conjugated systems have tuneable band gaps (Eg) and redox properties, whilst offering the potential for flexibility and low cost. In this thesis, the macromolecular compounds and their low molecular weight precursors were characterised by determining their electrochemical and optical properties which were measured using a series of techniques such as: cyclic voltammetry; UV/vis spectroscopy; emission spectroscopy; spectroelectrochemistry; Raman spectroscopy and thermal analyses. Chapter 2 Presents thiophene copolymers with electroactive nitrogen heterocycles. In section 1, a series of monomers containing heteropentalene mesomeric betaine derivatives were characterized. In particular the 3,4-ethylenedioxythiophene (EDOT) derivative (9) was successfully electropolymerised, yielding a polymer with small optical and electrochemical Eg. In Section 2 the characterisation of EDTT, 3-hexylthiophene and EDOT units (17, 18 and 19 respectively) along with their benzothiadiazole (BT) copolymers are shown. Interesting changes in planarity were observed between the PEDOT and PEDTT compounds. Section 3 and 4 produced many EDOT/thiophene derivatives from phenanthroline and [Ru(bpy)2]) as the core unit. (20-26) All polymers exhibited lower electrochemical Eg when compared to their monomers. Compound 26 was polymerised with high oxidative stability to anodic conditions, however, monomer 25 did not polymerise, due to the domination of the strong RuII/RuIII oxidation process. Section 5 shows bis-EDOT pyridine based monomers (27 and 28). Monomer 28 displayed significant effect of the intramolecular charge transfer (ICT) process and lower electrochemical Eg. Three are new compounds 29, 30 and 31 in the section 6, BODIPY cores with two EDOT, thiophene and EDTT units respectively. When all were compared, Compound 29 showed red shift in the absorption spectra, due to stronger electron donating effect of EDOT. Chapter 3: In section 1 the optical and electrochemical properties of three oligofluorene substituted DPP macromolecules (32, 33, 34) and the core precursors (35, 36, 37 and 38) were investigated. The absorption spectra of all compounds in CH2Cl2 revealed two peaks attributed to π-π* transition of quaterfluorene arms and the absorption of DPP core. Compound 33 exhibited a higher LUMO level compared to the other compounds, which was attributed to the effects of the hexyldecyl and phenyl groups. Section 2 describes six new C3-symmetric compounds containing BT units and truxene core (41-46). The UV-absorption spectra of compounds 41-45, reveal an ICT band which is hypsochromically shifted in the case of compound 41 and is not resolved for compound 46. Compounds 41-44 exhibited a good agreement between electrochemical and optical Eg, while a significant difference between those of compound 46 indicates the poor HOMO-LUMO overlap. Chapter 4 A novel processing methodology was used to fabricate multi-layer organic electronic devices by employing electropolymerisation to form a PEDOT/PEDTT bi-layer. The fabricated device did not exhibit any distinctive photo-response when it was assessed in a diode configuration. This was due to inefficient charge separation at the donor- acceptor interface.
- Resource Type
- Note
- Author name on cover: Saadeldin Elamin Taher Elmasly.
- DOI
- Date Created
- 2013
- Former identifier
- 1002047
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