Synthesis of Fluorinated <b>O‑IDTBR</b> Acceptors for Organic Solar Cells

Nonfullerene acceptors have led to remarkable advances in the efficiency and stability of organic photovoltaic devices (OPVs). Halogenation at key sites of molecular and polymeric acceptors can often enhance performance by affecting packing and phase separation with the donor. Here, we report on the synthesis and characterization of acceptors based on benzothiadiazole, a rhodanine derivative, and fluorinated indaceno[1,2-<i>b</i>:5,6-<i>b</i>′]dithiophene with octyl side chains (<b>O-IDTBR</b>). We report routes for one and two fluorine atom addition to the indacenodithiophene core (<b>1F-O-IDTBR</b>, <b>2F-O-IDTBR</b>) and compare the performance of organic solar cells with active layers composed of a polymer donor and <b>O-IDTBR</b>, <b>1F-O-IDTBR</b>, or <b>2F-O-IDTBR</b>. Solar cells based on <b>1F-O-IDTBR</b> outperform other devices due to higher short-circuit currents and fill factors, even though the open-circuit voltage is modestly lower when compared to <b>O-IDTBR</b> devices.