Perfluorophenyl-Incorporated Ferrocene: A Non-Volatile Solid Additive for Boosting Efficiency and Stability in Organic Solar Cells

In this study, we designed and synthesized a new non-volatile solid additive FcF10 by integrating two pentafluorophenyl (C6F5) groups into the cyclopentadienyl (CP) rings of ferrocene (Fc) through ester linkages. The FcF10 with a three-dimensional (3D) framework facilitated morphological optimization in the PM6:Y6 system through a combination of π···π, F···π, and F···F interactions between the CP and C6F5 rings in FcF10 and the C6F2 rings in Y6. The FcF10-incorporated (3.75 wt %) PM6:Y6-based solar cell device achieved a higher power conversion efficiency (PCE) of 17.00%, with a Voc of 0.85 V, a Jsc of 27.35 mA cm–2, and an FF of 73.29%, compared to the pristine PM6:Y6 device. These improvements are attributed to the formation of a favorable active layer morphology, which enhances exciton dissociation and charge transport while reducing bimolecular and trap-assisted recombination. The FcF10 additive facilitates non-covalent interactions with Y6, such as F···F, F···π, and π···π interactions between the Cp and C6F5 rings in FcF10 and the FIC end groups in Y6. These supramolecular interactions improve molecular stacking and crystallinity within the Y6 domain, as evidenced by red-shifted Y6 absorption, reduced π–π stacking d-spacing, and increased coherence lengths of Y6. Furthermore, the PM6:Y6:FcF10 device demonstrates superior thermal stability, retaining 88% of its initial PCE after prolonged thermal annealing at 85 °C. Overall, the incorporation of FcF10 achieves an optimized and stable donor–acceptor morphology, offering a promising approach for high-performance and thermally stable organic photovoltaics.