Rahul Somvanshi
A research team at Northwestern University has created a protective coating that triples the lifespan of perovskite solar cells under harsh conditions, according to their study published in Science on November 22, 2024. The new amidinium-based coating proves 10 times more resistant to decomposition compared to standard ammonium-based coatings.
The solar cells achieved 26.3% power conversion efficiency and retained 90% of their initial efficiency after being tested under harsh conditions, demonstrating a T90 lifetime three times longer than before when exposed to heat and light.
“State-of-the-art perovskite solar cells typically have ammonium ligands as a passivation layer,” said Yi Yang, the study’s first author. “But ammonium tends to break down under thermal stress. We did some chemistry to convert the unstable ammonium into a more stable amidinium.”
The research addresses a critical challenge in solar technology. While silicon remains the primary material for solar cells, its production costs stay high as efficiency approaches its upper limits. Perovskite offers a cost-effective alternative but has faced durability issues when exposed to sunlight, temperature changes, moisture, and humidity.
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The team’s solution involves amidinium ligands – stable molecules that interact with perovskite to provide lasting defect protection. These molecules, structured with a central carbon atom bonded to two amino groups, distribute electrons evenly, making them more resilient in harsh conditions.
Professor Edward Sargent, who directs the Paula M. Trienens Institute for Sustainability and Energy at Northwestern, noted: “The primary barrier to the commercialization of perovskite solar cells is their long-term stability. But due to its multi-decade head start, silicon still has an advantage in some areas, including stability. We are working to close that gap.”
Recent developments in the field show growing momentum. UK-based Oxford PV reported achieving 28.6% efficiency with a commercial-size perovskite tandem cell in May 2023, while combining perovskite with traditional silicon technology in tandem cells may push efficiencies higher.
The research received support from First Solar, the Department of Commerce, the National Institute of Standards and Technology, and the US Department of Energy. It forms part of Northwestern’s Generate pillar within the Trienens Institute Six Pillars of Decarbonization initiative, focusing on developing high-efficiency multi-junction solar cells and next-generation materials.
