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Design, syntheses and structure-property relationships of benzazole and isoindigo comprising conducting polymers/

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2019
Göker, Seza
Donor–acceptor (D–A) conjugated polymers have been widely used for potential applications such as organic light emitting diodes, solar cells, electrochromic devices and organic field effect transistors. Benzazole comprising conducting polymers are popular for the last few decades since they can be used as low-band-gap donor materials because of their strong intramolecular charge transfer characteristics and excellent photovoltaic performances. Strong electron-donating and withdrawing building blocks are necessary to lower the band gaps and HOMO energy levels of D–A polymers. Alkoxy substitution to the acceptor groups provides polymers better solubility and higher molecular weight whereas fluorine substitution increases the strength of the acceptors via lowering electron density. In this thesis, 2,1,3-benzazole moieties were substituted with alkoxy and fluorine groups. Benzazole and isoindigo were coupled with several donor groups via both Stille and Suzuki polycondensation reactions to investigate structure-property relationships. On the other hand, Direct Heteroarylation Polymerization (DHAP) was also performed to obtain new polymers via an eco-friendly method. Molecular weights of polymers were investigated with GPC analysis. Oxidation and reduction behavior of the polymers were conducted using cyclic voltammetry. Polymers were used as active layers in optoelectronic applications. The effect of thermal and solvent annealing on morphology were determined. After optimizing thickness and morphologies of polymer:PCBM, device production and current/voltage property measurements were performed in a nitrogen filled glove box system. The analysis of the photovoltaic devices ITO/ PEDOT:PSS/Polymer: PCBM/ Metal) were achieved by means of the energy conversion efficiency measured under standard AM 1.5G illumination.