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 cm², 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.