Research Paper: Dual Interface Modification for Reduced Nonradiative Recombination in n–i–p Methylammonium-Free Perovskite Solar Cells
Scientific Summary
This study aimed to overcome charge extraction losses and instability in perovskite solar cells (PSCs) by investigating a dual interface modification strategy in n−i−p methylammonium-free Pb-based PSCs. The researchers employed 4-fluorophenethylammonium (4FPEA) cations with various halide counteranions (iodide, bromide, and chloride) to modify both the buried (electron-transporting layer/perovskite) and top (perovskite/hole-transporting layer) interfaces. The main goal was to improve surface quality, enhance carrier dynamics, and reduce nonradiative recombination, which are critical for device efficiency and stability. The research found that while all studied counteranions effectively passivated defects and reduced recombination, leading to improved performance up to 20% efficiency, the selection of the counteranion was crucial for long-term stability.
Key Findings and Conclusions
The optimal interface modification with 4FPEA-I (iodide counteranion) not only enabled champion PSCs to surpass 20% efficiency but also demonstrated remarkable operational stability, maintaining performance over extended periods. In stark contrast, modifiers based on bromide and chloride, despite showing initial efficiency gains, severely compromised device robustness, leading to rapid degradation due to halide segregation. Specifically, devices with 4F-I/I showed significantly improved stability, losing only about 17% efficiency after 550 hours of maximum power point tracking, whereas 4F-I/Br and 4F-I/Cl devices decayed much faster. The iodide-based modification enhanced open-circuit voltage (VOC) and fill factor (FF) primarily by reducing interfacial recombination processes and improving electrical contact quality.
Why it matters
These findings are highly significant for advancing perovskite solar cell technology, as they provide a comprehensive surface engineering strategy to achieve both high efficiency and long-term stability—a major challenge for PSC commercialisation. The study critically highlights the often-neglected importance of the counteranion's nature in interface modifiers, revealing that non-native halides like Br− and Cl− can introduce new degradation pathways via halide segregation in iodide-pure perovskites. This work offers crucial insights for designing robust surface modifiers and presents a simple, reproducible dual interface modification strategy to produce efficient and stable methylammonium-free PSCs.
Publication Details
Rodriguez-Perez, J.J., Esparza, D., Ans, M., Contreras-Solorio, D.A., Diaz Perez, T., Rodriguez-Pereira, J., Barea, E.M., Zarazua, I., Prochowicz, D., Akin, S., Martinez-Pastor, J.P., Pascual, J., Mora-Seró, I. and Turren-Cruz, S.-H. (2025), Dual Interface Modification for Reduced Nonradiative Recombination in n−i−p Methylammonium-Free Perovskite Solar Cells. ACS Appl. Mater. Interfaces, 17, 8610−8618. https://doi.org/10.1021/acsami.4c20462.
Fluxim Tools Used
Fluxim Litos setup was utilised to conduct accelerated aging tests and maximum power point (MPP) tracking measurements. This enabled the researchers to precisely monitor the long-term operational stability of the perovskite solar cells under controlled conditions, including 1 sun equivalent illumination in an N2 atmosphere at controlled temperatures (25 °C or 45 ± 5 °C). The controlled and systematic stability assessment provided by the Fluxim Litos setup was essential for revealing the critical differences in degradation behaviour between devices modified with various halide counteranions, thereby underpinning the study's key conclusions regarding material robustness.