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For scalable perovskite solar cells (PSCs), deposition of a homogeneous and high-quality perovskite film on a large area (>100 cm2) is a prerequisite. Conventional solutions for spin-coating on small areas usually contain polar aprotic solvents with high boiling point, which is difficult to adopt for large-area bar coating because of the uncontrollable and slow drying process due to the strong interaction between polar aprotic solvent and Lewis acidic PbI2 or perovskite. Thus, the precursor solution plays a vital role in the success of large-area coating. Here we report a coating solution suitable for large-area perovskite films. The coating solutions prepared via gas-mediated solid–liquid conversion contain preformed perovskite clusters as confirmed by rotational mode of methylammonium cation in the PbI3– framework from Raman spectroscopy. CH3NH3PbI3 (MAPbI3) films formed by D-bar coating within 20 s on the area over 100 cm2 exhibit tetragonal/cubic superlattice structure with highly preferred orientation in the entire film, which results in average power conversion efficiency (PCE) of 17.01% and best PCE of 17.82%.
Jeong et al. (Mon,) studied this question.