Benzodithiophene‐Fused Perylene Bisimides as Electron Acceptors for Non‐Fullerene Organic Solar Cells with High Open‐Circuit Voltage

Tandem‐junction organic solar cells require solar cells with visible light photo‐response as front cells, in which an open‐circuit voltage ( V oc ) above 1.0 V is highly demanded. In this work, we are able to develop electron acceptors to fabricate non‐fullerene organic solar cells (NFOSCs) with a very high V oc of 1.14 V. This was realized by designing perylene bisimide (PBI)‐based conjugated materials fused with benzodithiophene, in which Cl and S atom were introduced into the molecules in order to lower the frontier energy levels. The fused structures can reduce the aggregation of PBI unit and meanwhile maintain a good charge transport property. The new electron acceptors were applied into NFOSCs by using Cl and S substituted conjugated polymers as electron donor, in which an initial power conversion efficiency of 6.63 % and a high V oc of 1.14 V could be obtained. The results demonstrate that the molecular design by incorporating Cl and S atom into electron acceptors has great potential to realize high performance NFOSCs.