Crystallization Control for Ambient Printed FA‐Based Lead Triiodide Perovskite Solar Cells

Abstract Upscalable printing of high‐performance and stable perovskite solar cells (PSCs) is highly desired for commercialization. However, the efficiencies of printed PSCs lag behind those of their lab‐scale spin‐coated counterparts owing to the lack of systematic understanding and control over perovskite crystallization dynamics. Here, the controlled crystallization dynamics achieved using an additive 1‐butylpyridine tetrafluoroborate (BPyBF₄) for high‐quality ambient printed α‐formamidinium lead triiodide (FAPbI₃) perovskite films are reported. Using in situ grazing‐incidence wide‐angle X‐ray scattering and optical diagnostics, the spontaneous formation of α‐FAPbI₃ from precursors during printing without the involvement of δ‐FAPbI₃ is demonstrated. The addition of BPyBF₄ delays the crystallization onset of α‐FAPbI₃, enhances the conversion from sol‐gel to perovskite, and reduces stacking defects during printing. Therefore, the altered crystallization results in fewer voids, larger grains, and less trap‐induced recombination loss within printed films. The printed PSCs yield high power conversion efficiencies of 23.50% and 21.60% for a 0.09 cm^–2area device and a 5 cm × 5 cm‐area module, respectively. Improved device stability is further demonstrated, i.e., approximately 94% of the initial efficiency is retained for over 2400 h under ambient conditions without encapsulation. This study provides an effective crystallization control method for the ambient printing manufacture of large‐area high‐performance PSCs.