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

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, we report the controlled crystallization dynamics achieved using an additive 1-butylpyridine tetrafluoroborate (BPyBF 4 ) for high-quality ambient printed α-formamidinium lead triiodide (FAPbI 3 ) perovskite films. Using in situ grazing-incidence wide angle X-ray scattering and optical diagnostics, we demonstrate the spontaneous formation of α-FAPbI 3 and sol-gel from precursors during printing without the involvement of  δ-FAPbI 3 . The addition of BPyBF 4 delays the crystallization onset of α-FAPbI 3 , 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 0.09 cm 2 -area devices and 5 cm × 5 cm-area modules, 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. This article is protected by copyright. All rights reserved.