Morphology Control for Efficient Nonfused Acceptor‐Based Organic Photovoltaic Cells

Abstract Non‐fused electron acceptors have huge advantages in fabricating low‐cost organic photovoltaic (OPV) cells. However, morphology control is a challenge as non‐fused C─C single bonds bring more molecular conformations. Here, by selecting two typical polymer donors, PBDB‐TF and PBQx‐TF, the blend morphologies and its impacts on the power conversion efficiencies (PCEs) of non‐fused acceptor‐based OPV cells are studied. A selenium‐containing non‐fused acceptor named ASe‐5 is designed. The results suggest that PBQx‐TF has a lower miscibility with ASe‐5 when compared with PBDB‐TF. Additionally, the polymer networks may form earlier in the PBQx‐TF:ASe‐5 blend film due to stronger preaggregation performance, leading to a more obvious phase separation. The PBQx‐TF:ASe‐5 blend film shows faster charge transfer and suppressed charge recombination. As a result, the PBQx‐TF:ASe‐5‐based device records a good PCE of 14.7% with a higher fill factor (FF) of 0.744, while the PBDB‐TF:ASe‐5‐based device only obtains a moderate PCE of 12.3% with a relatively low FF of 0.662. The work demonstrates that the selection of donors plays a crucial role in controlling the blend morphology and thus improving the PCEs of non‐fused acceptor‐based OPV cells.