Benzodithiophene and benzotriazole bearing alternating copolymers, effect of thiophene and bithiophene _-bridges on photovoltaic properties

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2016
İstanbulluoğlu, Çağla
In this study, two novel 1,2,3-benzotriazole and benzodithiophene bearing alternating copolymers were synthesized via Stille coupling reaction. Benzodithiophene was used as the donor moiety due to its strong electron donating ability and planar structure. Benzotriazole moiety was incorporated as the acceptor unit due to its electron deficient nature. Moreover, thiophene (P1) and bithiophene (P2) conjugated moieties were incorporated between donor and acceptor units in order to investigate the effect of π-bridge. Electrochemical, spectroelectrochemical and kinetic studies were performed. Since both polymers revealed ambipolar character, HOMO-LUMO energy levels were calculated from cyclic voltammograms. As a result of kinetic studies, good stabilities and low switching times were recorded. Moreover, bithiophene bearing copolymer showed enhanced percent transmittance and low switching time at NIR region when compared with thiophene bearing polymer. Organic photovoltaic applications of the polymers were conducted with a device structure of ITO/PEDOT:PSS/POLYMER:PC70BM/LiF/Al The analysis of the photovoltaic devices was performed under standard AM 1.5G illumination. Alkyl chains on the donor and acceptor moieties enhanced the solubility of the polymers in organic solvents. Thickness and morphology of the devices were examined via AFM and TEM studies. As a result of several optimization studies, power conversion efficiencies were reached to 2.12 % and 1.20 % for P1 and P2, respectively. P1 was used as active layer for OLED applications which were constructed with a device structure of ITO/PEDOT:PSS/P1/LiF/Al. Red emissive OLED was produced with CIE coordinates (x,y) of 0.65, 0.34, respectively.

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Citation Formats
Ç. İstanbulluoğlu, “Benzodithiophene and benzotriazole bearing alternating copolymers, effect of thiophene and bithiophene _-bridges on photovoltaic properties,” M.S. - Master of Science, Middle East Technical University, 2016.