A triazoloquinoxaline and benzodithiophene bearing low band gap copolymer for electrochromic and organic photovoltaic applications

By Hacioglu, Serife O.; Unlu, Naime A.; Aktas, Ece; Hizalan, Gonul; Yildiz, Esra D.; Cirpan, Ali; Toppare, Levent
Published in Synthetic Metals NULL 2017

Abstract

Abstract A new triazoloquinoxaline and benzodithiophene based copolymer was synthesized to investigate its electrochemical, optical and photovoltaic behaviors. According to the polymer design, combination of two acceptor units (benzotriazole and quinoxaline) which contribute imine bonds to the structure and a triazoloquinoxaline unit for enhancing electron accepting ability was pursued. As a result of electrochemical studies, the copolymer {PTQBDT} has a low lying {HOMO} energy level as ?5.23 eV which increases the chemical stability of the resulting polymer and leads to a higher Voc. In addition, the copolymer has an ambipolar character with two well-defined redox couples in the n-doped state and multichromic behavior. In the context of optical studies, {PTQBDT} has wide absorption range in the visible region with a tail in the {NIR} region, which yields a low band gap of 1.20 eV. Organic photovoltaic devices were designed using {PTQBDT} (the electron donor) and {PC71BM} (the electron acceptor) for the preliminary studies. The resulting device exhibits a power conversion efficiency of 2.0% with a current density of 8.07 mA cm?2, an open-circuit voltage of 0.45 V, and a fill factor of 55%. The carrier mobility of the {PTQBDT} was calculated as 3.00

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