Inverted perovskite solar cells (IPSCs) are widely considered the future of next-generation photovoltaics due to their high efficiency, low cost, and ease of manufacturing. To achieve record-breaking efficiencies, scientists typically use self-assembled monolayers (SAMs) with just one molecule thick to extract positive charges (holes) from the perovskite layer. However, these conventional ultra-thin interfaces are extremely fragile. They are prone to molecular disorder and weak bonding, leading to severe performance degradation under heat and operational stress.
A collaborative research team from the Southern University of Science and Technology (SUSTech) and The Hong Kong Polytechnic University (PolyU) has proposed a new solution. In a study published in Science Bulletin , the researchers introduce a “multidimensional spatial confinement” strategy that fundamentally rethinks how SAM molecules are designed and stabilized at buried interfaces.
Conventional SAM molecules typically rely on flexible alkyl linkers to connect their anchoring groups to functional moieties. While effective for charge extraction, these flexible linkers make the molecular layer susceptible to thermal disorder, solvent-induced desorption, and mechanical degradation. The new strategy replaces this flexibility with rigidity.
The team designed a custom molecule, MeO-PABDCB, featuring a rigid phenylene backbone that promotes dense, ordered in-plane packing through π–π interactions. At the same time, the molecule forms strong multidentate chemical bonds with the underlying indium tin oxide (ITO) electrode and establishes robust interactions with the overlying perovskite layer. Together, these effects spatially confine the molecules both laterally and vertically, effectively creating a “molecular lock” at the interface.
This locked molecular architecture not only suppresses molecular desorption and disorder but also improves the quality of the perovskite film grown on top. Devices incorporating the spatially confined SAM exhibit reduced interfacial defects, lower residual strain in the perovskite layer, and more efficient hole extraction. As a result, the inverted perovskite solar cells achieved power conversion efficiency of 26.54% with a high fill factor of 86.4%. More importantly, the devices demonstrated outstanding durability, retaining approximately 90% of their initial efficiency after 1000 hours of continuous operation and 250 thermal cycles between −40 and 85 ℃.
The study establishes spatial confinement as a general molecular design principle for stabilizing ultra-thin functional interfaces. By showing that structural robustness and electronic performance can be achieved simultaneously, this work provides a practical pathway toward more reliable perovskite-based optoelectronic devices.
Science Bulletin
Experimental study