Reexamining the Role of Solution-Cast Ferroelectric Polymer Interlayer toward Enhanced Efficiency and Stability in Conventional Organic Solar Cells

Interfacial modification is crucial for achieving efficient and stable organic solar cells (OSCs). Herein, an N,N-dimethylformamide (DMF) solution-cast poly­(vinylidene fluoride-co-trifluoroethylene) (P­(VDF-TrFE)) interlayer was applied to enhance the efficiency and stability of a range of OSCs, and the underlying mechanism was revealed via morphological and device physics studies. DMF rinse during the P­(VDF-TrFE) interlayer casting process strengthens π–π stacking of the active layer with fibril aggregation, optimized phase separation, and vertical component distribution, while the P­(VDF-TrFE) interlayer with rich diploes contributes to increased surface potential and internal electric field. The synergistic effect of the P­(VDF-TrFE) interlayer and DMF rinse increases the PCEs of PM6:IT-4F, PM6:C5–16, and PM6:L8-BO OSCs from 12.7, 17.9, and 18.2% to 13.1, 18.7, and 18.8%, respectively. Additionally, OSCs containing the P­(VDF-TrFE) interlayer also showed improved storage stability.