Tetrafluoroquinoxaline based polymers for non-fullerene polymer solar cells with efficiency over 9%

In order to increase the power conversion efficiency (PCE) of non-fullerene polymer solar cells (PSCs), the absorption spectra of donor and acceptor should be complementary for efficient light harvesting. Here, we designed and synthesized two types of medium bandgap polymers in which two dimension-conjugated benzodithiophene (BDT) (BDTT and BDTPS) was used as the electron donating units and tetrafluoroquinoxaline (ffQx) was used as electron accepting unit, namely PffQx-T and PffQx-PS, for the application as donor in the PSCs with a popular non-fullerene small molecule ITIC as acceptor. Their optical, electrochemical and photovoltaic properties were well investigated. Under AM 1.5G, 100 mW/cm(-2), all the PSCs with the ffQx-based polymers as donor exhibited PCEs over 8% (8.47% for PffQx-T and 9.12% for PffQx-PS). To the best of our knowledge, the PCE of 9.12% is the highest value for BDT-Qx fullerene-free PSCs to date, which is even higher than that of fullerene-based devices.