Synergistic passivation and stable carrier transport enable efficient blade-coated perovskite solar cells fabricated in ambient air

Abstract

Perovskite solar cells (PSCs) continue to grapple with efficiency and long-term stability limitations stemming from crystalline defects (such as halide vacancies, undercoordinated Pb²⁺ defects, etc.) and interfacial energy-level misalignments. To mitigate these challenges, we design and introduce Bis(3-fluorophenyl) disulfide (SF) as a multifunctional interfacial modifier at the perovskite (PVK) and electron transport layer (ETL) interface. The SF molecule engages in a dual-site synergistic passivation mechanism: sulfur atoms form robust Pb–S bonds with undercoordinated Pb²⁺ ions, while fluorine atoms occupy iodine vacancies and form hydrogen bonds with FA⁺/MA⁺ cations. This dual interaction suppresses ion migration and halide volatilization, significantly reducing surface defect density and trap states, thereby improving carrier transport. Stroboscopic scattering microscopy (stroboSCAT) reveals superior long-term carrier dynamics in SF-treated films, which retain ∼86% of their initial maximum carrier diffusion coefficient after 2000 hours in ambient air, far surpassing control devices (∼41%). Notably, after three months of ambient storage, SF-modified perovskite film exhibits an approximately threefold higher average carrier diffusion coefficient (0.0247 ± 0.0028 cm² s⁻¹) than the control group (0.0079 ± 0.0017 cm² s⁻¹), underscoring perovskite film quality enhancement. This sustained diffusion coefficient improvement directly correlates with elevated device stability and performance retention. Correspondingly, blade-coated PSCs incorporating SF, fabricated under ambient conditions, reach a peak power conversion efficiency (PCE) of 24.60% with an open-circuit voltage (V_oc) of 1.17 V. Furthermore, the hydrophobic nature of SF's fluorinated aromatic rings provides an effective barrier against moisture, enabling devices to maintain 96.8% of their initial PCE after 2000 hours under 30–40% relative humidity, far exceeding the control's 60% (after 1200 hours) retention. Collectively, these findings demonstrate that SF enables a robust, scalable strategy for concurrently enhancing efficiency and environmental durability in PSCs, while also offering valuable molecular design insights for future multifunctional interfacial engineering using bidentate passivating agents.