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New interfacial SAM coating enables over-30% power conversion efficiency and improved durability without moisture-free fabrication
A Korean research team has developed an interfacial coating material needed for the mass production of high-efficiency perovskite·silicon tandem solar cells, a next-generation photovoltaic technology. The new material allows the fabrication of tandem solar cells with power conversion efficiencies above 30% using standard processes carried out in ambient air that exposes perovskite to moisture and oxygen, a known weakness of the material. This is seen as lowering the barrier to large-scale manufacturing.
Ulsan National Institute of Science and Technology (UNIST) announced on the 11th that Distinguished Professor Sang Il Seok of the Department of Energy and Chemical Engineering and Professor Kyung Jin Choi’s group in the Department of Materials Science and Engineering, in collaboration with a research team at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, have developed a new electrical interfacial coating material. The results were published on the 1st (local time) in the international journal 'Nature Photonics'.
Perovskite·silicon tandem solar cells are high-efficiency devices made by stacking a perovskite cell on top of a silicon cell. The perovskite top cell first absorbs the shorter-wavelength portion of sunlight, while the silicon bottom cell absorbs the remaining light, achieving higher efficiency than single-junction silicon cells. China has also joined the race to secure leadership in this technology.
The team improved the material used in the thin contact layer that is first deposited on the electrode surface before stacking the perovskite layer. The contact layer must adhere uniformly so that the perovskite solution spreads evenly, which in turn reduces defects that degrade efficiency.
Conventional self-assembled monolayer (SAM) coating layers are thin and transparent, resulting in low optical losses, but they fail to coat the electrode surface uniformly when moisture is present in the air and are easily disrupted during deposition of the perovskite solution. Because high efficiencies could only be achieved in specialized equipment that blocks moisture and oxygen, SAMs had been a major obstacle to reducing the cost of large-area production.
The researchers solved this problem by adding the molecules glycerol dimethacrylate (GDMA) and 1-acetylguanidine (AG) to the SAM. GDMA helps the molecules spread more uniformly across the electrode surface and suppresses the washing away of the SAM during the perovskite solution process. AG serves to reduce interfacial defects.
With the newly developed material applied, the tandem solar cell achieved a power conversion efficiency of 31.72% even when fabricated under ambient atmospheric conditions. This is the highest reported efficiency worldwide for tandem solar cells manufactured in air. The independently certified efficiency is 31.36%.
Durability has also improved. Even without any encapsulation protecting the cell surface, the device retained more than 92% of its initial performance after 600 hours of exposure to hot air at 85°C. It also maintained over 90% efficiency after 1,000 hours of continuous illumination with strong light that mimics sunlight. The approach can also increase manufacturing yield when producing single-junction perovskite solar cells.
Professor Choi said, "This research aligns with the government's 'K-Moonshot Project' goal of developing ultra-high-efficiency multi-junction tandem solar cells with a substantial performance lead," adding, "It will make a significant contribution to the commercialization of next-generation solar cells."
Professor Seok stated, "To commercialize high-efficiency tandem solar cells, we must address not only performance but also process reproducibility and production costs," and continued, "By demonstrating that uniform interfacial thin films and high reproducibility can be achieved even in ordinary ambient air with moisture, this work will provide the technological foundation needed to extend the technology to large-area manufacturing processes."
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– doi.org/10.1038/s41566-026-01925-z
