Substituent Effects of Electron-Withdrawing and Electron-Donating Groups on Photovoltaic Properties of Quinoxaline-Based Polymers

Herein, a string of quinoxaline-based D–A-type polymers possessing either electron-withdrawing or electron-donating groups were developed to explore their impact on the photovoltaic efficiency of the polymers. Once the reference polymer PBF-CF₃Qx was prepared, extra fluorine atoms and methoxy units were selectively added on the 6,7-positions of the quinoxaline unit of the PBF-CF₃Qx reference to provide two objective polymers, PBF-CF₃QxF and PBF-CF₃QxM, respectively. Owing to the significant influence of the existing electron-withdrawing or electron-donating substituents, each polymer displayed considerably discernible optical, electrochemical, and morphological features. Moreover, the conventional nonfullerene photovoltaic devices based on PBF-CF₃QxF and PBF-CF₃QxM exhibited superior power conversion efficiencies of 11.37 and 11.18%, respectively, compared to the device based on the PBF-CF₃Qx reference 6.96%). These results emphasize the significance of electron-withdrawing and electron-donating substituents in quinoxaline-based polymers for controlling their intrinsic and photovoltaic attributes.