Natural Amino Acid Enables Scalable Fabrication of High‐Performance Flexible Perovskite Solar Cells and Modules with Areas over 300 cm2

Abstract Upscaling large‐area formamidinium (FA)‐based perovskite solar cells (PSCs) has been considered as one of the most promising routes for the commercial applications of this rising photovoltaics technology. Here, a natural amino acid, phenylalanine (Phe), is introduced to regulate the nucleation and crystal growth process of the large‐scale coating of FA‐based perovskite films. Better film coverage and larger grain sizes are observed after adding Phe. Moreover, it is found that Phe can effectively passivate defects within perovskite films and suppress the nonradiative recombination due to the strong interaction with under‐coordinated Pb 2+ ions in the perovskite films. Rigid PSCs based on the blade‐coated perovskite films containing Phe obtain a champion efficiency of 21.95%. The corresponding unencapsulated devices also exhibit excellent ambient stability, retaining 95% of their initial efficiencies after storage in the glovebox at 20 °C for 1000 h. Further, the strategy is applied to fabricate flexible PSCs and modules on polyethylene terephthalate/indium doped tin oxide substrates via slot‐die coating. Phe modified flexible devices achieve outstanding efficiencies of 20.21%, 12.1%, and 11.2% with aperture areas of 0.10, 185, and 333 cm 2 , respectively. The strategy here has paved a promising way for the large‐scale production of flexible PSCs.