Conjugated polymers with benzothiadiazole and benzotriazole moieties for polymer solar cells

In this study four novel random polymers, comprising benzothiadiazole and benzotriazole as the accepting units and benzodithiophene as the donor unit, were synthesized via Stille polymerization reaction. Moreover, effects of fluorine atom and π bridges on optical, electrochemical and optoelectronic properties were investigated. Optical band gap values of P1, P2, P3 and P4 were found as 1.78 eV, 1.72 eV, 1.63 eV and 1.73 eV, respectively. Characterization of polymers via UV–Vis–NIR spectroscopy, cyclic voltammetry (CV), gel permeation chromatography (GPC) and thermal analysis were carried out. Polymer solar cells (PSCs) were constructed and characterized in N2 filled glove box. While the polymers act as electron donors, PC71BM was the electron acceptor in the PSCs with the device structure of ITO/PEDOT:PSS/Polymer:PC71BM/LiF/Al. As a consequence of measurements under standard AM 1.5 G illumination (100 mW/cm2), the highest power conversion efficiency values were recorded as 4.10% 3.84%, 1.60% and 3.83% for P1, P2, P3 and P4 based PSCs, respectively.