Fast Solidification and Slow Growth Strategy for High-Performance Quasi-2D Perovskite Solar Cells

Smooth perovskite film with high crystallinity and vertical orientation is highly favored for high-performance quasi-2D perovskite solar cells (PVSCs), yet limited by the critical balance between nucleation and crystal growth. To address this issue, here a fast solidification and slow growth (FSSG) strategy is developed to effectively optimize the film morphology. The fast solidification enables a smooth, pinhole-free film, while slow growth allows it to further ripen into high-crystallinity film. This process is enabled by the low-boiling point solvent system, that is, acetonitrile, with high-boiling point additives, that is, NH 4 SCN and CH 3 NH 3 Cl. Compared to the traditional method, uniform film with a larger grain/crystallite size as well as better crystallinity can be easily fabricated through this FSSG strategy. As a result, the quasi-2D PVSCs based on (GA) 2 (MA) 4 Pb 5 I 16 processed with the FSSG strategy show a champion power conversion efficiency of 20.44%, as well as 19.08% for large-area (1 cm 2 ) devices, which suggest the capability of the FSSG strategy for up-scaled PVSC fabrication. Therefore, this work opens a new avenue toward morphology control of PVSCs for practical applications.