Multifunctional Ionic Liquid Assisted Crystallization Regulation and In Situ Defect Passivation for High-Performance Perovskite Solar Cells

Perovskite solar cells (PSCs) have become a highly anticipated research direction in the field of next-generation photovoltaic technology due to their excellent photoelectric conversion performance. One core issue for high-performance PSCs is to suppress the non-radiative recombination caused by defects in the perovskite layer and at the interfaces. In this work, a novel functionalized sulfonate-based ionic liquid, 1-ethyl-3-methylimidazolium methyl sulfonate (EMIM-MS), is introduced for in situ defect passivation during the perovskite crystallization process. For the anionic part of EMIM-MS, the -SO 3 − group can form coordination with Pb 2+ , and the -CH 3 groups can form hydrogen bonds with I−. Coupled with the formation of hydrogen bonds between EMIM-MS and formamidinium (FA + ), high-quality perovskite films with large crystal size and low defect density are achieved. In addition, due to its large molecular size, EMIM-MS can be squeezed to the surface during annealing, playing an important role in passivating defects at the interfaces. Therefore, the efficiency of PSC based on EMIM-MS is significantly improved to 25.48% from the controlled 22.24%, and the long-term storage and wet heat stability are also improved. This strategy provides valuable insights for defect passivation and helps promote the industrialization of PSC.