Perovskite solar cells have emerged as promising next-generation photovoltaic technologies, with rapidly advancing power conversion efficiencies and strong potential for scalable manufacturing. However, the performance and durability of inverted perovskite solar cells remain closely linked to the quality of the buried interface between the self-assembled molecular (SAM) hole-transport layer and the perovskite absorber. Poor interfacial adhesion, inefficient charge extraction, and defects within the perovskite lattice can promote non-radiative recombination and accelerate device degradation. To address these challenges, researchers from Henan University, the Institute of Process Engineering of the Chinese Academy of Sciences, The Chinese University of Hong Kong, and Beijing Institute of Technology have developed a molecular bridging strategy that simultaneously improves interfacial charge transport, defect passivation, and long-term device stability.
Why This Interface Matters
SAM-based hole-transport layers offer important advantages for inverted perovskite solar cells, including favorable energy-level alignment and low-temperature processing. Nevertheless, their molecular aggregation and incomplete substrate coverage can compromise the contact with the perovskite layer. Meanwhile, undercoordinated Pb 2+ ions and A-site vacancies at the buried interface create defect sites that facilitate charge recombination and ion migration. Addressing these interconnected problems requires an interfacial modifier capable of strengthening adhesion while maintaining efficient electronic communication between adjacent layers.
Innovative Design and Mechanism
The research team introduced two sulfonate-based molecules, sodium methyl allyl sulfonate (SMAS) and 2-formylbenzenesulfonic acid sodium salt (2-FAS), as functional interlayers between the SAM and perovskite. Both molecules improve substrate wettability, regulate perovskite crystallization, and passivate interfacial defects through coordination between their sulfonate groups and undercoordinated Pb 2+ ions. Notably, 2-FAS offers an additional advantage: its benzene ring forms strong π–π interactions with the conjugated SAM molecules, creating an effective molecular bridge that facilitates hole extraction and interfacial charge transfer. Its Na⁺ ions can also occupy A-site vacancies in the perovskite lattice, helping suppress ion migration and phase transitions while reinforcing structural stability.
Outstanding Performance
The optimized 2-FAS-modified inverted perovskite solar cells achieve a champion power conversion efficiency of 26.21%, with an open-circuit voltage of 1.164 V and a fill factor of 86.15%. This substantially exceeds the efficiencies of the untreated control (24.58%) and SMAS-modified devices (25.41%). More importantly, unencapsulated devices retain 90.06% of their initial efficiency after 4500 hours of storage in a nitrogen atmosphere, outperforming both the control and SMAS-based devices.
Applications and Future Outlook
By combining molecular-level interfacial bridging, defect passivation, and lattice stabilization, this work establishes a practical strategy for addressing multiple performance-limiting factors in inverted perovskite solar cells. The use of low-cost, readily available sulfonate molecules also offers advantages for accessible interface engineering. These findings provide a promising foundation for developing more efficient and durable perovskite photovoltaic devices, bringing their potential for long-term practical applications closer to reality.
Nano-Micro Letters
News article
A Buried Sulfonate Molecular Bridge for Synchronous Charge Transport and Defect Passivation in High‑Performance Perovskite Solar Cells
14-Aug-2026