An Ortho‐Bisalkyloxylated Benzene‐Based Fully Non‐fused Electron Acceptor for Efficient Organic Photovoltaic Cells

Abstract To develop the low‐cost nonfullerene acceptors (NFAs), two fully non‐fused NFAs (TBT‐2 and TBT‐6) with ortho ‐bis((2‐ethylhexyl)oxy)benzene unit and different side chains onto thiophene‐bridges are synthesized through highly efficient synthetic procedures. Both acceptors show good planarity, low optical gaps (≈1.51 eV), and deep highest occupied molecular orbital levels (≤‐5.77 eV). More importantly, the single‐crystal structure of TBT‐2 shows compact molecular arrangement due to the existence of intramolecular interactions between adjacent aromatic units and strong π – π stacking between intermolecular terminal groups. When the two acceptors are fabricated organic photovoltaic (OPV) cells by combining with a wide optical gap polymer donor, the TBT‐6 with strong crystallization forms large domain sizes in bulk heterojunction (BHJ) blend. As a result, the TBT‐6‐based OPV cell shows a low power conversion efficiency (PCE) of 9.53%. In contrast, the TBT‐2 with proper crystallization facilitates morphological optimization in the BHJ blend. Consequently, the TBT‐2‐based OPV cell gives an outstanding PCE of 13.25%, which is one of the best values among OPV cells with similar optical gaps. Overall, this work provides a practical molecular design strategy for developing high‐performance and low‐cost electron acceptors.