Optical and electrochemical properties of benzotriazole and benzodithiophene containing alternating copolymers

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2021-2-15
Yıldırım, Merve
The demands of humanity are changing and enhancing day by day with the increasing population. One of the most significant needs is energy in the world; but not only energy is a requirement, but also green energy is a necessity due to global pollution. As a result, organic photovoltaic devices have been developed and investigated in recent years. In this study, two new donor-acceptor (D-A) type copolymers with different π-bridges were designed and synthesized for organic photovoltaic devices. In this study, polymers contain benzotriazole moiety as the acceptor unit, alkoxyphenyl substituted benzodithiophene moiety as the donor unit with selenophene and thiophene as the π-bridges were synthesized. The characteristic features of synthesized polymers P1and P2 were investigated via electrochemical, optical, spectroelectrochemical and kinetic studies. The optical band gaps were found as 1.83 eV and 1.81 eV for P1 and P2, correspondingly. Moreover, HOMO and LUMO energy levels of P1 were recorded as -5.25 eV/ -3.34 eV; HOMO and LUMO energy levels of P2 were recorded as -5.38 eV/-3.48 eV, respectively. The electronic band gap (Egel) values of P1 and P2 were calculated as 1.91 eV and 1.90 eV. The polymers were used as the donor materials and PC71BM as the acceptor material in the active layer of bulk heterojunction organic photovoltaic devices. The photovoltaic features of P1 and P2 based organic solar cells were examinedITO/PEDOT:PSS/Polymer:PCBM/LiF/Al device structure and measured under standard AM 1.5 G illumination (100 mW/cm2). The highest power conversion efficiency was recorded as 1.40% with a JSC of 4.39 mA/cm2, a VOC of 0.71 V and a FF of 45% for P1. The highest power conversion efficiency of bulk heterojunction solar cell device based on P2 was recorded as3.57% with a JSC of 9.67 mA/cm2, a VOC of 0.71 V and a FF of 52%.
Citation Formats
M. Yıldırım, “Optical and electrochemical properties of benzotriazole and benzodithiophene containing alternating copolymers,” M.S. - Master of Science, Middle East Technical University, 2021.