Improvement of Formamidinium-based Ruddlesden–Popper Perovskite Solar Cells by Combined Co-Additives and Treatment Engineering Strategies

In this study, the effects of methylammonium chloride (MACl) and potassium iodide (KI) as additives in the fabrication of FA-based quasi-2D perovskite films (n=6) is investigated. We observed that K+ effectively suppresses iodide migration, thereby reducing hysteresis in the J-V curve. The effects of the additives on the film formation have been investigated by GD-OES and XRD. Using MACl additive further optimize the film formation, resulting in a reduced trap density, increased carrier lifetime, and extended diffusion length. The devices achieved a peak power conversion efficiency (PCE) of 19.18%, demonstrating both high efficiency and stability. Furthermore, passivating the perovskite surface using 4F-PEAI led to an improved power conversion efficiency (achieving 19.39%) and stability.