Syntheses and investigation of optoelectronic properties of benzothiadiazole and benzotriazole containing conjugated polymers

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2017
Keleş, Duygu
Benzothiadiazole is one of the most widely used acceptor units in Donor–Acceptor copolymers for organic solar cells (OSCs) with its strong electron withdrawing ability. It is also known that fluorine atom substitution directly to the backbone of conjugated polymers can improve the important parameters such as power conversion efficiency (PCE), open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) of OSCs. Besides benzothiadiazole, benzotriazole is another acceptor moiety which is used in OSCs frequently. In this study, two different random polymers, including benzothiadiazole and benzotriazole as the accepting units and benzodithiophene as the donor unit, were synthesized via Stille polymerization reaction. Moreover, effects of fluorine atom on optical, electrochemical and optoelectronic properties were investigated. Optical band gap values of P1 and P2 were found as 1.78 eV and 1.72 eV, respectively. After characterization of polymers via UV-Vis-NIR spectroscopy, cyclic voltammetry (CV), gel permeation chromatography (GPC) and thermal analysis, the polymers were used to construct organic photovoltaic cells. Fabrication and characterization of them was performed in nitrogen-filled glove box system. While the polymers act as electron donor, PC70BM was electron acceptor in the OSCs which were constructed according to ITO/PEDOT:PSS/Polymer:PC70BM/LiF/Al. Morphology of Polymer:PC70BM blends was investigated with Atomic Force Microscopy (AFM). In consequence of measurement under standard AM 1.5 G illumination (100 mW/cm2), the highest power conversion efficiency was found as 4.13% for P1 and 3.80% for P2.

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Citation Formats
D. Keleş, “Syntheses and investigation of optoelectronic properties of benzothiadiazole and benzotriazole containing conjugated polymers,” M.S. - Master of Science, Middle East Technical University, 2017.