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, the controlled crystallization dynamics achieved using an additive 1-butylpyridine tetrafluoroborate (BPyBF4) for high-quality ambient printed alpha-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 alpha-FAPbI3 from precursors during printing without the involvement of delta-FAPbI3 is demonstrated. The addition of BPyBF4 delays the crystallization onset of alpha-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 x 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. The crystallization dynamics of alpha-formamidinium lead triiodide (alpha-FAPbI3) perovskites during ambient blade coating are manipulated by employing an additive 1-butylpyridine tetrafluoroborate (BPyBF4), resulting in the highly crystalline perovskite film with large grains, eliminated voids, and reduced defects. This enables the high power conversion efficiencies of 23.50% and 21.60% for a 0.09 cm2 area device and a 5 cm x 5 cm-area module, respectively.image

Automated summary

This study demonstrates the controlled crystallization dynamics of alpha-formamidinium lead triiodide (FAPbI3) perovskite films using an additive 1-butylpyridine tetrafluoroborate (BPyBF4) for high-performance and stable printed perovskite solar cells. The addition of BPyBF4 delays crystallization onset, enhances conversion to perovskite, and reduces defects in printed films, resulting in improved power conversion efficiencies and stability.