Ionic Liquid-Assisted MAPbI₃ Nanoparticle-Seeded Growth for Efficient and Stable Perovskite Solar Cells

With the rapid improvement of perovskite solar cells (PSCs), long-life operational stability has become a major requirement for their commercialization. In this work, we devised a pristine cesium-formamidinium-methylammonium (termed as CsFAMA) triple-cation-based perovskite precursor solution into the ionic liquid (IL)-assisted MAPbI₃ nanoparticles (NPs) through a seeded growth approach in which the host IL-assisted MAPbI₃ NPs remarkably promote high-quality perovskite films with large single-crystal domains, enhancing the device performance and stability. The power conversion efficiency (PCE) of the MAPbI₃ NP-seeded growth of MAPbI₃ NPs/CsFAMA-based PSCs is as high as 19.44%, which is superior to those of MAPbI₃ NPs and pristine CsFAMA films as the photoactive layer (9.52 and 17.33%, respectively). The long-term light-soaking and moisture stability of IL-aided MAPbI₃ NPs/CsFAMA-based devices (non-encapsulated) remain above 90 and 80%, respectively, of their initial output after 2 h of light illumination (1 sun) and 6000 h storage at ambient with a relative humidity range of 30-40%. The use of the IL-assisted MAPbI₃ NP-seeded growth for PSCs is a significant step toward developing stable and reliable perovskite photovoltaic devices.