Researchers at The Hong Kong University of Science and Technology have created a new way to build perovskite solar cells using a completely solvent-free vacuum process. The breakthrough, published in Nature Materials, achieves the first certified performance for this type of solar cell.
The new method solves a long-standing problem with vacuum-deposited perovskites, which previously formed low-quality crystals with defects. Professor Lin Yen-Hung, Assistant Professor in the Department of Electronic and Computer Engineering, led the team that developed a multi-source evaporation technique that creates highly ordered crystal structures.
Perovskite solar cells have attracted strong interest because they convert sunlight to electricity efficiently and could lower the cost of renewable power. Most high-performing versions today are made using liquid chemical solutions. But vacuum deposition—the same clean process used for OLED displays and optical coatings—offers a solvent-free alternative that coats large areas uniformly.
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The challenge was that perovskites made entirely through vacuum deposition formed poor crystal structures, making them unstable and prone to failure. Dr. Shen Xinyi, a postdoctoral researcher and first author of the study, and her team solved this by introducing a lead chloride “co-source” during thermal evaporation. This guides the perovskite crystals to grow in a uniform, face-up orientation that resists damage from light and heat.
Using this recipe, the team achieved 18.35% certified efficiency on a small test cell, with lab results reaching 19.3%. The cells also proved durable, retaining 80% of their peak performance after more than 1,000 hours under intense light and heat testing.
The technology works particularly well for tandem solar cells, which stack a perovskite layer on top of traditional silicon cells to capture more of the sun’s energy. The team built 1-cm2 perovskite-on-silicon tandem cells that achieved 27.2% efficiency. In an outdoor trial in Italy, these cells maintained about 80% of their initial performance after eight months of real-world operation.
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The method currently works on laboratory-scale devices of 0.25 to 1 square centimetre. Scaling up to commercial sizes while maintaining quality remains the next engineering challenge.
This development transforms vacuum deposition from a compromised alternative into a leading method for producing stable, high-performance perovskite solar cells. Because the process uses existing industrial equipment already common in thin-film manufacturing, it offers a direct path from laboratory research to factory production.
