Regulating the Nucleation Kinetics of Photovoltaic Perovskites via a Ternary Solvent Strategy Renders Efficient Solar Cells and Modules

Perovskite solar cells have undergone rapid improvement over the past decade, with their efficiency rivaling that of silicon-based solar cells. Nevertheless, the solvate-based phase transition leads to hardly controlled nucleation and thus inhomogeneous film formation. Herein, we propose a "host-guest-additive" ternary solvent strategy, aiming to regulate the processing window for photovoltaic perovskites. Our analysis shows that the optimized nucleation window is the most conducive factor for fabricating high-quality perovskite films. Furthermore, by the insertion of an additive, the degree of solvent-solute interaction can be tailored. The time window for nucleation of perovskite therefore is optimized, rendering improved surface flatness, uniformity, and grain sizes. Based on these findings, we fabricated solar cells, achieving a power conversion efficiency of 24.47%, a substantial improvement over the baseline performance of 22.31%. To further verify the availability of our strategy, we also made perovskite minimodules with an active area of 12.8 cm², which also showed improved efficiency from 18.99% to 20.86%. The 3D microscope reveals improved uniformity of the resulting perovskite film across monitored large areas, indicating the application of our ternary strategy for scaling up photovoltaic perovskites. We believe the findings unearthed here provide critical insights for systematically exploring synergistic multicomponent solvent effects in film formation of perovskites.