Researchers at the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) created a new perovskite ink. Uniquely, NREL says that the perovskite ink has a long processing window that could enable mass production of perovskite thin film for high-efficiency solar cells. While perovskite material has proven highly efficient at converting sunlight into electricity, the technology hasn’t reached beyond the lab.
Typically, a careful laboratory process of spin coating grows perovskite material upon a substrate. The technology for spin coating, unfortunately, can’t be scaled for high volume manufacturing. On the other hand, the highest performing devices formed with more scalable deposition methods still lag behind the performance of the best devices fabricated with spin coating.
The NREL scientists overcame this obstacle and detailed their method in a paper published in Nature Energy.
In Perovskite film fabrication coating of chemicals is deposited on a substrate and heated to complete the crystallization. The various steps often overlap, complicating the process. During one extremely critical stage, an antisolvent is added to extract the precursor chemicals, and thus create good quality crystals. The period during which this step can be performed is just seconds. However, with a new method, NREL researchers were able to keep that window open as long as 8 minutes, potentially enabling larger scale manufacturing.
The precursor perovskite ink included a chlorine-containing methylammonium lead iodide precursor along with solvent tuning, all of which was coupled with an antisolvent. The resulting ink could be deposited onto the substrate using either spin-coating or blade-coating with indistinguishable film morphology and device performance between the coating methods. Blade-coating is more attractive to manufacturers because it can easily be scaled up.
Using blade-coated absorbers, NREL scientists fabricated a four-cell perovskite module measuring about 12.6-square centimeters, 11.1 square centimeters of which were active with a stabilized efficiency of 13.3 percent.
M. Yang, Z. Li, M.O. Reese, et al. “Perovskite ink with wide processing window for scalable high-efficiency solar cells.” Nature Energy 2, 17038 (2017). doi:10.1038/nenergy.2017.38