Phosphate Ester‐Modified Acceptor Additives Enable Concurrent Vertical Morphology and Interfacial Engineering for Organic Solar Cells Approaching 21% Efficiency

Organic solar cells (OSCs) based on non-fullerene acceptors (NFAs) have progressed rapidly, yet further gains are constrained by coupled challenges in vertical morphology control and energy alignment at the acceptor-cathode interface. Here, a molecular engineering strategy is presented that installs strongly polar phosphate ester groups onto the inner alkyl chains of the benchmark NFA L8-BO, yielding two derivatives-1POE and 2POE. Employed as non-volatile solid additives during layer-by-layer processing, these molecules induce vertical composition redistribution to form a graded donor-acceptor-additive architecture. The resulting vertical profiling strengthens intermolecular interactions, raises surface…

• NN
  National Natural Science Foundation of China

  Awards: 22379101, 22422904
• NK
  National Key Research and Development Program of China

  Award: 2022YFB4200500