Researchers from UNIST (Ulsan National Institute of Science and Technology), KAUST (King Abdullah University of Science and Technology), the Chinese University of Hong Kong (Shenzhen) and Forschungszentrum Jülich have developed a process-tolerant interfacial engineering strategy that enables high-efficiency perovskite and perovskite/silicon tandem solar cells to be fabricated under ambient conditions, overcoming a known bottleneck in scalable manufacturing.
Self-assembled monolayers (SAMs) are widely used as hole-selective contacts in high-performance perovskite solar cells (PSCs) due to their excellent transparency and low parasitic absorption. However, conventional phosphonic-acid SAMs are highly sensitive to moisture, leading to poor surface coverage, inhomogeneity, and partial exposure of the transparent conductive oxide when processed in air. As a result, high-efficiency devices typically require fabrication in inert atmospheres, limiting throughput and increasing production cost. To address this limitation, the researchers designed a ternary self-assembled molecular contact that incorporates glycerol dimethacrylate (GDMA) and 1-acetylguanidine (AG) into the SAM system. GDMA plays a dual role: it acts as a co-solvent during deposition to improve wetting and film uniformity, and upon mild thermal curing, it forms a hydrophilic binary network that anchors the SAM robustly to the substrate. This network suppresses disruption of the monolayer during subsequent perovskite deposition. Meanwhile, AG is introduced to passivate interfacial defects, further improving charge selectivity and reducing recombination losses.
This molecular design directly addresses two critical failure modes of conventional SAMs under ambient processing: non-uniform coverage and instability during solution processing. By ensuring homogeneous coating of the electrode surface, the modified SAM enables uniform spreading of the perovskite precursor solution, which reduces defect formation in the overlying film and improves device reproducibility.
Using this approach, wide-bandgap PSCs fabricated entirely in ambient air achieved a power conversion efficiency (PCE) of 21.20% on a 1.00 cm² device area, with an open-circuit voltage of 1.28 V. When integrated into monolithic perovskite/silicon tandem architectures, the devices reached a PCE of 31.72% under ambient fabrication conditions, with a certified efficiency of 31.36%. For comparison, devices fabricated under inert conditions achieved 32.60%, indicating only a marginal performance gap despite the absence of controlled environments.
Beyond efficiency, the interfacial layer also delivers significant improvements in operational stability. Unencapsulated tandem devices retained more than 92% of their initial efficiency after 600 hours at 85°C in air, and maintained over 90% performance after 1,000 hours of continuous illumination under simulated sunlight. These results highlight the robustness of the interfacial network formed by GDMA and the defect passivation effect of AG.
The ability to fabricate high-efficiency tandem solar cells in ambient conditions represents a major step toward industrialization. By eliminating the need for glovebox processing while maintaining high performance and durability, the approach reduces both capital and operational costs and improves manufacturing scalability. In addition, the same interfacial strategy can enhance yield and reproducibility in single-junction perovskite solar cells.
Overall, the study demonstrates that tailored molecular engineering of SAM-based contacts can overcome long-standing environmental sensitivity issues, enabling high-efficiency perovskite photovoltaics compatible with industrial-scale fabrication.
