Green-Solvent-Processable Organic Photovoltaics with High Performances Enabled by Asymmetric Non-Fullerene Acceptors

In this work, two asymmetric non-fullerene acceptors (NFAs), BTP-EHBO-4F and BTP-PHD-4F, are designed to be applied in green-solvent-processable organic photovoltaics (OPVs). BTP-EHBO-4F and BTP-PHD-4F show good solubilities in green solvent o-xylene. As a result, PM6:BTP-EHBO-4F-based devices exhibit outstanding photovoltaic performances using o-xylene as a solvent. By comparison, due to the poor solubility of Y6 in o-xylene, PM6:Y6-based devices show poor performances. Owing to the favorable phase separation, molecule packing, and orientation observed from atomic force microscopy (AFM) and grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements, PM6:BTP-PHD-4F-based devices demonstrate a PCE of 15.91% with a V_OC of 0.87 V, a J_SC of 25.64 mA/cm², and an FF of 71.34%. Moreover, PM6:BTP-EHBO-4F-based devices exhibit an impressive PCE of 16.82% with a V_OC of 0.85 V, a J_SC of 26.12 mA/cm², and an FF of 75.78%, which is outstanding for OPVs using o-xylene as a solvent.