A Method for the Preparation of Highly Oriented MAPbI₃ Crystallites for High-Efficiency Perovskite Solar Cells to Achieve an 86% Fill Factor

The quality of the perovskite absorber is known to be the most crucial parameter for the photovoltaic performance of perovskite solar cells. By combining the one-step anti-solvent engineering method followed by gas blowing, MAPbI₃ film containing highly oriented multi-crystalline nanograins (150∼500 nm) was made first. A user-friendly, simple, large-throughput, and reproducible post-solvent annealing (made by treating the film with anti-solvent containing H₂O under spinning) was used to enlarge the perovskite grains up to 1.5 μm. Inverted (p-i-n) perovskite solar cells based on this highly ordered, large-grain MAPbI₃ film achieve the highest efficiency of 21% with an extremely high fill factor (FF) of 86%. The high-efficiency cell shows almost no current hysteresis and is stable under 1 sun illustration in a glovebox or standing in the ambient atmosphere (20∼25 °C, ca. 30% humidity) under room lighting (T5 lamp, 500 lux). A creative method combining the gas blowing with quick and simple post-treatment to prepare a highly oriented MAPbI₃ film with large multi-crystalline grains to achieve excellent photovoltaic performance was demonstrated. This creative film-preparation method was also successfully applied to fabricate large area MAPbI₃ film for high-efficiency perovskite mini-modules. Being able to control the crystallization and growth of perovskite crystallites definitely makes the fabrication of perovskite solar cells more reproducible.