Morphology Optimization of Perovskite Films for Efficient Cells and Modules through Solvent Engineering

N‐Methyl‐2‐pyrrolidone (NMP) has become one of the mainstream Lewis base ligand solvents for the fabrication of high‐quality FA‐based perovskite films. However, the NMP‐based perovskite films with small grain sizes always own a mirror surface which will increase the reflection of light and limit the current of perovskite solar cells (PSCs). In this work, 2‐pyrrolidone (NP) with a higher boiling point and stronger binding to precursor components is introduced into the precursor solution to improve the crystallization and morphology of perovskite. Finally, a rougher perovskite film with a larger grain size can be fabricated via an optimized NP and NMP mixed ligand solvent. Based on this strategy, the champion device achieved a power conversion efficiency (PCE) of 24.20% (certified PCE of 23.81%) and 22.13% on an aperture area of 0.0875 and 22.96 cm 2 , respectively. In addition, the introduction of NP enhances the humidity and light stability of the film, and the device retained 94.1% of its initial efficiency after 120 h.