How crystallization additives govern halide perovskite grain growth
Timo Maschwitz, Lena Merten, Feray Ünlü, Martin Majewski, Fatemeh Haddadi Barzoki, Zijin Wu, Seren Dilara Öz, Cedric Kreusel, Manuel Theisen, Pang Wang, Maximilian Schiffer, Gianluca Boccarella, Gregor Marioth, Henrik Weidner, Sarah Schultheis, Tim Schieferstein, Dawid Gidaszewski, Zavkiddin Julliev, Ekaterina Kneschaurek, Valentin Munteanu, Ivan A. Zaluzhnyy, Florian Bertram, Anaël Jaffrès, Junjie He, N. R. Ashurov, Martin Stolterfoht, Christian M. Wolff, Eva Unger, Selina Olthof, Geert Brocks, Shuxia Tao, Helen Grüninger, Olivier J. J. Ronsin, Jens Harting, Andreas Kotthaus, Stefan F. Kirsch, Sanjay Mathur, Alexander Hinderhofer, Frank Schreiber, Thomas Riedl, Kai Oliver Brinkmann
Abstract
The preparation of perovskite solar cells from the liquid phase is a cornerstone of their immense potential. However, a clear relationship between the precursor ink and the formation of the resulting perovskite is missing. Established theories, such as heterogeneous nucleation and lead complex colloid formation, often prove unreliable, which has led to an overreliance on heuristics. Most high-performing perovskites use additives to control crystallization. Their role during crystallization is, however, elusive. Here, we provide evidence that typical crystallization additives do not predominantly impact the nucleation phase but rather facilitate coarsening grain growth by increasing ion mobility across grain boundaries. Drawing from the insights of our broad, interdisciplinary study that combines ex and in situ characterization methods, devices, simulations, and density function theory calculation, we propose a concept that proves valid for various additives and perovskite formulations. Moreover, we establish a direct link between additive engineering and perovskite post-processing, offering a unified framework for advancing material design and process engineering.