Tailored multi-functional molecular chain-based ferrocene derivative for efficient and stable perovskite solar cells

Under the stimulation of external factors, the ions with small activation energies could escape from the surface of perovskite, aggravating the defects at the interfaces and deteriorating the perovskite solar cells (PSCs). Here, we report a novel strategy utilizing a tailored organometallic molecule (bis-ferrocenyl-carboxylate-hexadecafluorodecyl, namely Fc-16 F) interlayer to functionalize the perovskite/hole transport layer interface, which simultaneously blocks the migration pathways of ions and facilitate the charge extraction at the interface. The electron-absorbing substituents (carboxyl groups and a long C-F chain) are introduced to strengthen the redox properties of ferrocene units, limit self-migration, and enhance hydrophobicity. With the strengthened oxidation driving force and the tight and dense hydrogen bond networks formed between Fc-16 F and organic cations, Fc-16 F could efficiently recover the Pb, I vacancies, inhibit the diffusion of defect-induced by-products (I₂), and stabilize the components on the surface. The champion device modified with Fc-16 F interlayer yields a remarkable power conversion efficiency (PCE) of 23.02% as well as superior humidity and long-term stabilities. The Fc-16 F-modified PSCs retain an outstanding 83.3% of its initial PCE over 1200 h under high humidity (60% RH) and retain over 90% of its initial PCE after aging in the N₂ atmosphere for over 2000 h.