Fused-ring acceptors based on quinoxaline unit for highly efficient single-junction organic solar cells with low charge recombination

Abstract

Two non-fullerene small molecule acceptors (TFQ-F and TFQ-Cl) based on quinoxaline unit were designed and synthesized for efficient organic solar cells (OSCs). These two acceptors showed intense absorption up to 900 nm and high thermal stabilities with decomposition temperatures over 360 °C due to their fused-ring skeletons. TFQ-F and TFQ-Cl are the A-D-A′-D-A type acceptors (A/A′ for acceptor unit and D for donor unit). TFQ-F and TFQ-Cl have the same D-A′-D fragment, which was flanked with different ending groups. The effect of different ending groups on their photophysical properties, electrochemical behaviors, micro-structures and charge recombination properties of active layers, and device performance were investigated systematically. PM6 with the complementary absorption to the two acceptors was used as the donor material. The pristine PM6:TFQ-F blend films displayed the optimal morphologies as revealed by AFM and TEM measurement. Organic solar cells based on PM6:TFQ-Cl blend film showed high JSC of 25.19 mA/cm2 and PCE of 13.2%. The Voc, JSC and PCE for PM6:TFQ-F film based device were 0.857 V, 23.70 mA/cm2 and 13.51%, respectively. The dependence of VOC/JSC on various light intensities indicated that PM6:TFQ-F/Cl based device had low charge recombination.